26th International Symposium on Spin Physics (SPIN2025)

21 Sep 2025, 14:00 → 26 Sep 2025, 18:00 Asia/Shanghai

The 26th international symposium on spin physics (SPIN2025) will be held in Qingdao (Tsingtao), Shandong Province, China, from Monday, September 22nd, to Friday, September 26th, 2025. This symposium is a leading event that unites both theorists and experimentalists working in the fields of high-energy and nuclear spin physics. Held biennially, the event rotates between Asia, Europe, and America. 

Since its inception in 2000, the conference has merged the High Energy Spin Symposia and the Nuclear Polarization Conferences. Previous editions took place in Charlottesville, VA (2008), Jülich, Germany (2010), Dubna, Russia (2012), Beijing, China (2014), Urbana-Champaign, IL (2016), Ferrara, Italy (2018), Matsue, Japan (2021), and Durham, NC (2023).

2025 is the international year of Quantum Science and Technology and spin has been such an important part of the development of quantum physics. 2025 also marks a century since George E. Uhlenbeck and Samuel A. Goudsmit proposed the concept of spin for fundamental particles. One can access and download the “Century of spin” poster realized by the BNL Media & Communication at https://www.bnl.gov/centuryofspin.

The symposium will be organized by Shandong University, bringing together physicists in spin physics to Qingdao, a picturesque coastal city in eastern China, to share the latest advancements in the field. Participation of young physicists is strongly encouraged.

Scientific topics:

• Nucleon helicity structure
• Spin physics in nuclear reactions and nuclei
• Three-dimensional structure of the nucleon: transverse momentum dependent parton distributions
• Three-dimensional structure of the nucleon: generalized parton distributions and form factors
• Low energy spin physics with lepton, photon and hadron probes
• Fundamental symmetries and spin physics beyond the standard model
• Acceleration, storage and polarimetry of polarized beams
• Polarized ion and lepton sources and targets
• Future facilities and experiments
• Application of spin and nuclear polarization techniques
• Spin in heavy ion collisions
• Quantum computing and artificial intelligence

Important deadlines:

• Early registration opens on February 1st, 2025
• Hotel reservation opens on February 1st, 2025
• Abstract submission opens on February 1st, 2025
• Abstract submission closes on June 30th, 2025 (extended to August 31st, 2025) 
• Notification for accepted submission is expected by August 31st, 2025
• Early-bird registration closes on July 31st, 2025
• Free cancellation closes on August 15th, 2025
• Hotel reservation closes on August 31st, 2025
• Registration closes on August 31st, 2025

 

photo.JPG

SPIN2025_1st_Circular.pdf

SPIN2025_2nd_Circular.pdf

SPIN2025_3rd_Circular.pdf

SPIN2025Handbook.pdf

SPIN2025Poster.pdf

Sunday, 21 September

Registration and reception

Monday, 22 September

Plenary

Conveners: Yu-gang Ma (Fudan University) , Qinghua Xu (Shandong University)

1 Openning and welcome

Speaker: Shucai Li

2 From the discovery of spin to the quantum anomalous Hall effect --- to celebrate 100 years of spin

Speaker: Qi-Kun Xue (Tsinghua University)

10:10 Photo and Coffee break

3 Nucleon spin structure from inclusive scattering

Speaker: Xiaochao Zheng (University of Virginia)

main_A1_spin2025 1.pdf

4 Nucleon helicity distributions

Speaker: Emanuele Roberto Nocera (Università degli Studi di Torino and INFN Torino)

NOCERA_SPIN2025.pdf

Lunch

Plenary

Conveners: Alessandro Bacchetta (University of Pavia and INFN) , Naohito Saito

5 TMD experiments

Speaker: Fulvio Tessarotto

tessarotto_SPIN2025_TMD_Experiments.pdf

6 GPD experiments

Speaker: Daria Sokhan (University of Glasgow)

2Spin25_GPDs_Daria.pdf

15:20 Coffee break

7 SIDIS experiment and fragmentation functions

Speaker: Anselm Vossen (Duke University)

SPIN_2025_SIDIS_Talk_Vossen_V4.pdf

SPIN_2025_SIDIS_Talk_Vossen_V4.pptx

8 Spin physics at BESIII

Speaker: Hai-Bo Li (IHEP CAS)

Spin-BESIII-2509-Qingdao-v4.pptx

9 Lattice calculation of TMDs

Speaker: Wei Wang (Shanghai JiaoTong University)

TMD_LQCD.pdf

Tuesday, 23 September

3-dimensional structure of nucleon - TMD

Conveners: Christopher Dilks, Andrea Signori, Ting Lin

Conveners: Ting Lin (Shandong University) , Yuxiang Zhao (University of Science and Technology of China (USTC))

10 The SoLID-TMD Program at Jefferson Lab

The Solenoidal Large Intensity Device (SoLID) is an advanced spectrometer under development in Hall A at Jefferson Lab. Designed for high-luminosity operation (10³⁷–10³⁹ cm⁻²s⁻¹) with both polarized (NH3 and 3He) and unpolarized hydrogen and deuterium targets, SoLID features large acceptance and full azimuthal coverage. It will fully exploit the capabilities of the 12 GeV CEBAF upgrade and is optimized for a broad range of physics programs, including precision measurements in semi-inclusive deep inelastic scattering (SIDIS) for three-dimensional nucleon imaging in momentum space. Several highly rated SIDIS experiments have been approved to extract transverse momentum dependent parton distribution functions (TMDs) with unprecedented precision. The current 11 GeV electron beam will allow SoLID to explore TMDs in the important valence quark region, and the proposed future 22 GeV upgrade will extend its kinematic range significantly. In this presentation, we will introduce the SIDIS program at Jefferson Lab using SoLID, highlight associated parallel run-group opportunities, and present updated impact on extracting TMDs.

Speaker: Zhihong Ye (Tsinghua University)

SoLID_Spin2025_ZYe.pdf

11 Fragmentation function studies at BESIII

Abstract: Fragmentation Function (FF) plays a crucial role in describing the hadronization process. We report the measurements of normalized differential cross sections of inclusive pi0 and Ks production as a function of hadron momentum at six energy points with q^2 transfer from 5 to 13 GeV^2 at BESIII. The results with a relative hadron energy coverage from 0.1 to 0.9 significantly deviate from several
theoretical calculations based on existing fragmentation functions.

Speaker: Yateng Zhang (ZZU)

fragmentationytspin.pdf

12 Spin asymmetries of eta mesons in polarized proton collisions at PHENIX

For the last two decades, the PHENIX collaboration at Brookhaven National Laboratory has explored nuclear spin physics by leveraging the Relativistic Heavy Ion Collider’s unique ability to collide transversely or longitudinally polarized protons. Eta meson production is a particularly practical channel at PHENIX as their detection is possible through diphoton decays in both the central and forward rapidity electromagnetic calorimeters, allowing for a broad reach in both transverse momentum and Feynman-x. In this talk, I will present a recent PHENIX measurement of the transverse single spin asymmetry of eta mesons in the forward rapidity region. This observable is directly sensitive to the twist-3 quark-gluon correlators in both the initial and final state. A comparison between the measurement and a theoretical prediction of the initial-state contribution to the asymmetry suggests that the final state plays a vital role in the generation of the large observed asymmetry. I will also present the status of a measurement of the longitudinal double spin asymmetry from our high luminosity 510 GeV data set. This observable probes the contribution of the gluon polarization to the proton’s spin, providing a complementary final state to the earlier PHENIX neutral pion measurement which, for the first time, provided clear evidence of a nonzero gluon polarization.

Speaker: Devon Loomis

SPIN2025_PHENIX_Loomis.pdf

13 Measurement of Transverse Single Spin Asymmetry ($A_{N}$) of Neutral Pions ($\pi^0$) using Transversely Polarized $p^\uparrow p$ collisions at STAR

In proton-proton ($pp$) collisions involving a transversely polarized proton beam and an unpolarized proton beam, a left-right or azimuthal asymmetry is observed in the distribution of final-state scattered particles. The experimentally measurable quantity is known as the Transverse Single Spin Asymmetry ($A_N$). This asymmetry arises from fundamental Transverse Momentum Dependent (TMD) mechanisms involving the interplay between transverse momentum and spin of the participating partons and handrons. While perturbative Quantum Chromodynamics (pQCD) theory predicts very small $A_N$, experimental observations suggest otherwise. Previous measurements of $A_N$ for neutral pions ($\pi^0$) at mid-rapidity ( $|\eta |< 1$) indicate that it is consistent with zero; however, at forward rapidities ($3.3 < \eta < 5.5$), significantly larger values have been observed. Consequently, measurements in the intermediate rapidity range ($1.0 < \eta < 2.0$) are crucial for providing a comprehensive understanding of $A_N$ and the underlying physics processes. The objective of this talk is to present the status of $A_N$ for $\pi^0$ using the STAR Endcap Electromagnetic Calorimeter (EEMC) from STAR Run 2015 transversely polarized $p^{\uparrow}p$ collisions at a center-of-mass energy of 200 GeV. The EEMC's azimuthal coverage across the pseudorapidity range of $1.09 \le \eta \le 2.00$ will enable the determination of $A_N$ at intermediate rapidities, and provide a complete picture of the $A_N$ distribution.

Speaker: Ananya Paul (University of California, Riverside)

SPIN2025_AnanyaPaulTalk_v9.pdf

10:00 Coffee Break

14 Recent results on TMDs from the MAP collaboration

This talk will present recent results on the determination of transverse momentum distributions by the MAP collaboration, with a particular emphasis on the flavor dependence of unpolarized TMDs, on the helicity TMD, and on machine-learning methods."

Speaker: Alessandro Bacchetta (University of Pavia and INFN)

Qingdao_SPIN2025.pdf

15 ART25 (a recent global TMD fit)

After the conceptual improvements to transverse momentum dependent (TMD) extractions of a flavour dependent ansatz as well as a more robust propagation of uncertainties onto the resulting TMD functions in ART23, the following work ART25 is a state of the art determination of the unpolarised TMD parton distribution functions and -fragmentation functions such as the Collins-Soper kernel via a global fit on the available data.

With a simplistic model we achieve a good result for the fit and describe the data in the relevant phase space, provided by measurements of the semi-inclusive DIS and the Drell-Yan process.

In my talk I am going to review the framework of the extraction,
present the results of this work
and comment on aspects on which this type of fits can improve on.

Speaker: Valentin Moos (NYCU)

main.pdf

16 Transverse momentum dependent helicity distributions

In this talk, I will present the first extraction of TMD helicity distributions, by analyzing double spin asymmetry data from SIDIS.

Speaker: Dr Ke Yang (山东大学)

杨科-2025-09-青岛.pdf

17 Transverse Momentum Dependent Parton Distributions and EicC Projection

We present the global analysis of Sivers functions, worm-gear distribution functions, transversity distribution functions, and Collins fragmentation functions within the transverse momentum dependent factorization. This analysis encompasses the latest data from SIDIS, DY, and W±/Z-boson production processes. In addition, based on a combined analysis of world data and simulated data, we quantitatively demonstrate the impact of the proposed Electron-Ion Collider in China on precise determinations of the Sivers, worm-gear and transversity distributions.

Speaker: Hongxin Dong (NNU)

Spin2025.pptx

3-dimensional structure of nucleon: GPD and FF: 02

Conveners: Barbara Pasquini, Sznajder Pawel, Stefan Diehl

Convener: Paweł Sznajder (National Centre for Nuclear Research, Poland)

18 Recent results of Baryon electromagnetic form factors at BESIII

At BESIII, the electromagnetic form factors (EMFFs) and the pair production cross sections of various baryons have been studied. The proton EMFF ratio |GE/GM| is determined precisely and line-shape of |GE| is obtained for the first time. The recent results of neutron EMFFs at BESIII show great improvement comparing with previous experiments. Cross sections of various baryon pairs (Lambda, Sigma, Xi, Lambdac) are studied from their thresholds. Anomalous enhancement behavior on the Lambda and Lambdac pair are observed. The relative phase of EMFFs for Lambda and Sigma+ are measured for the first time.

Speaker: Mi Wang (USTC)

spin25report_20250923.pdf

19 A Proposal to Measure Nucleon Axial-Vector Form Factor using Polarized Electron Beam

The form factors are important physical quantities that characterize
the internal structure of a nucleon. In the classical picture, it
corresponds to the Fourier transform of the nucleon's three-dimensional
density distribution. Among them, the electromagnetic form factors are
the most well-known, with thousands of high-precision experimental data
accumulated to date. The axial form factor is another essential type of
nucleon form factor. It is not only a crucial input for neutrino
oscillation experiments but also plays a significant role in
constraining the nucleon's generalized parton distribution functions.
However, compared to the electromagnetic form factors, the axial form
factor suffers from both a scarcity of data and limited precision.
Traditionally, its measurement relies on neutrino scattering and
near-threshold pion electroproduction, both of which face inherent
limitations. In this talk, I will present a novel measurement scheme and
experimental concept based on high-precision polarized electron beams,
which promises to overcome many of the shortcomings of existing methods.
This experiment is planned to be carried out at Jefferson Lab and is
currently in the design phase.

Speaker: Weizhi Xiong (Shandong University)

AxialFF_SPIN_2025.pdf

20 Nucleon 3D intrinsic spin structure from the weak-neutral axial-vector form factors

We present the first systematic study of the relativistic intrinsic spin structure of a general spin-$1/2$ hadron in position space. We show in particular that the slope of the nucleon axial form factor $G_A^Z(Q^2)$ in the forward limit, conventionally denoted as $R^2_A \equiv -\frac{6}{G_A^Z(0) } \frac{ \text{d} G_A^Z(Q^2) }{\text{d} Q^2} \Big|_{Q^2=0} $ in the literature, does not faithfully characterize the size of the weak axial charge content of the nucleon in the Breit frame, but corresponds instead to a contribution to the nucleon 3D spin radius $r_\text{spin} \equiv \sqrt{\langle r_\text{spin}^2 \rangle}$, with $\langle r_\text{spin}^2 \rangle = R_A^2 + \frac{1}{4M^2}\left( 1 + \frac{G_P^Z(0)}{G_A^Z(0) } \right)$. We derive explicit expressions for the spin radius in different frames, and find in general additional contributions that depend on both the nucleon mass and the forward values of the axial-vector form factors $G_A^Z(0)$ and $G_P^Z(0)$. We also show that the second-class current contribution associated with the induced pseudo-tensor form factor $G_T^Z(Q^2)$ does not contribute in fact to both the nucleon axial and spin radii. Our work paves a new and direct way for investigating the nucleon 3D intrinsic spin structures using the weak-neutral axial-vector form factors $G_{A,P,T}^Z(Q^2)$ extracted from elastic (anti)neutrino-nucleon scattering data, or calculated in lattice QCD and various models and approaches.

Speaker: Dr Yi Chen (Tsinghua University & University of Science and Technology of China)

Spin2025_YiChen_v2.pdf

21 Probing Meson Structure via Lattice QCD: EMFF at high $Q^2$ and GPD

We present lattice QCD computations addressing crucial aspects of meson internal structure through electromagnetic form factors (EMFFs) and generalized parton distributions (GPDs). Utilizing physical masses and fine lattices, we calculate pion and kaon EMFFs at momentum transfers up to approximately 10 and 28 GeV$^2$, respectively, achieving good agreement with available experimental data at low momentum transfers and providing essential ab-initio benchmarks for upcoming high-energy experiments. Additionally, we compute the x-dependent valence pion GPDs at zero skewness across various momentum transfers by employing advanced renormalization and matching schemes, and also deliver a three-dimensional image of the pion structure in impact-parameter space.

The talk is based on
[1] H.T.Ding, X.Gao, A.D.Hanlon et al., Phys.Rev.Lett. 133 (2024) 18, 181902
[2] H.T.Ding, X.Gao, S.Mukherjee et et al., JHEP 02(2025)056

Speaker: Heng-Tong Ding (Central China Normal University)

HTD_Spin2025.pdf

10:00 Coffee break

22 QED nuclear medium effects at EIC energies

We present the first calculation of quantum electrodynamics (QED) nuclear medium effects under the experimental conditions of future Electron-Ion Collider (EIC) experiments. While prior studies have predominantly focused on elastic scattering, our investigation extends to the more complex scenarios of inelastic processes within a nuclear medium. For lead nuclei, our findings suggest that the cross-section corrections due to QED nuclear medium effects could be substantial, reaching or exceeding the level of experimental precision. We estimate the dominant source of the uncertainties associated with our formalism by varying the scale of the atomic physics where the screening of the electric field of the nucleus happens. This calculation offers a path to a more precise extraction of the process-independent non-perturbative structure of nuclei.

Speaker: Sasha Tomalak (Institute of Theoretical Physics, Chinese Academy of Sciences)

Tomalak_Spin_2025_September.pdf

23 Nucleon Structure from Basis Light-Front Quantization : Status and Prospects

We report recent advancements in understanding nucleon structure within the Basis Light-Front Quantization (BLFQ) framework—a fully relativistic, nonperturbative approach to solving quantum field theories. Starting with the leading Fock sector $|qqq\rangle$ and an effective light-front Hamiltonian incorporating confinement and one-gluon exchange, BLFQ has successfully described key nucleon observables. The framework has since been extended to include the next-to-leading Fock sector $|qqqg\rangle$, enabling studies of gluonic contributions to the nucleon's internal structure, including gluon helicity, orbital angular momentum, and three-dimensional imaging through GPDs and TMDs. Most recently, BLFQ has achieved a significant milestone by computing nucleon light-front wavefunctions as eigenstates of the QCD Hamiltonian without an explicit confining potential. These calculations, including Fock sectors up to $|qqqq\bar{q}\rangle$, allow towards first-principles predictions of quark and gluon matter densities, helicity and transversity distributions, and spin observables, showing qualitative agreement with experimental and phenomenological results. Together, these developments highlight BLFQ’s growing capacity to provide an increasingly complete and realistic picture of nucleon structure grounded in QCD.

Speaker: Chandan Mondal (Institute of Modern Physics)

Chandan_Spin_2025.pdf

24 Lattice calculation of Baryon Light-cone Distribution Amplitudes

We present a lattice QCD calculation for the leading-twist Light-cone Distribution Amplitudes (LCDAs) of the Lambda and Proton, within the framework of Large-momentum Effective Theory (LaMET). The numerical computation employs CLQCD ensembles with stout smeared clover fermions and a Symanzik gauge action. In order to obtain reliable results in both perturbative and non-perturbative regions, we adopt a new Hybrid renormalization scheme and carry out simulations at 4 different lattice spacings: a = {0.052, 0.068, 0.077, 0.105} fm. To access the large momentum regime and facilitate matching to LCDAs, we simulate the quasi-Distribution Amplitudes (quasi-DAs) with hadron momenta Pz around 1~3 GeV. After renormalization and extrapolation, we present results for the distribution of momentum fractions for the two light quarks in Lambda and Proton.

Speaker: Mu-hua Zhang (SJTU)

Baryon LCDA from LQCD.pdf

Application of spin and nuclear polarization techniques: Block 1

Conveners: Xin Tong, Tianhao Wang

Conveners: Junpei Zhang (高能所) , Tianhao Wang (中科院高能物理研究所)

25 Polarized neutron application at the China Spallation neutron source

Neutron beams generated at the China Spallation Neutron Source (CSNS) are dedicated for material characterization through scattering process. Polarization can be introduced before and after the neutron scatter with the sample so that neutron magnetic dipole interaction with local magnetization can be observed, know as polarized neutron scattering. The polarized neutron can be expanded to nuclear physics through observing the polarized neutron and polarized nuclei reaction. Some interesting interference and resonance method for can also be achieved through carefully arranged neutron polarization precession.
In this talk, we introduce the recently development of the polarized neutron experiment capability at the CSNS, focusing on effort of setting up polarized neutron for exotic measurement. Specifically, we give detailed demonstration on setting up polarization and analysis for eV level neutron for the purpose of symmetry violation measurement. Development of in-house made neutron adiabatic radio-frequency and its application on Ramsey resonance method shall also be introduced.

Speaker: Tianhao Wang (中科院高能物理研究所)

Polarized neutron application at the China Spallation neutron source.pptx

26 Current developments of polarized sources and polarimeter at FZ Jülich and further applications

A better theoretical understanding of the quantum mechanical processes in spin filter for the separation of metastable hydrogen atoms in individual hyperfine substates enables a number of new applications. For example, it is now possible to build a new generation of Lamb-shift polarimeter that can separate not only α but also the β states with $m_J = -1/2$. This opens up completely new possibilities for the search of hydrogen atoms in forbidden substates after the bound beta decay of the neutron. At the same time, corresponding simulations also provide the parameters for designing a Lamb-shift polarimeter for $^3He^+$ ions. Furthermore, it has recently been shown that classical Lamb-shift polarimeter can determine the polarization, in addition to protons/deuterons and $H/D$ atoms, of $H_2/D_2$ molecules as well as all possible ion beam species, i.e. $H_2^+/D_2^+/HD^+, H^-/D^-$ or even $H_3^+$.

In parallel, this knowledge might help to create a new type of optically pumped polarized source by transferring a laser-induced polarization of the rotational magnetic moment to the nucleons in $H_2/D_2$ and HD molecules. These techniques might also be used for the production and detection of polarized fuel for the enhancement of the energy output of nuclear fusion reactors or the production of hyperpolarized probes in medicine.

A recent application was a proof-of-principle measurement of the polarization conservation in $H_2$ molecules after recombination of polarized atoms in a carbon-coated storage cell, similar to the cell that is foreseen for a planned polarized target at the LHCb experiment. In addition, in some more exotic experiments the components of a Lamb-shift polarimeter can be used to detect axions or “dark hydrogen”.

Speaker: Dr Ralf Engels (Forschungszentrum Jülich)

Spin25.RalfEngels.pptx

27 Developement of polarized solid target for nuclear physics exteriment

I will present an overview of our activities on the study of the three-nucleon force using a polarized deuteron beam and a polarized proton target at RIKEN, with particular focus on the polarized proton target. We have developed the target system based on Dynamic Nuclear Polarization with photoexcited triplet electrons (Triplet-DNP), operating at 0.4 T and room temperature. Low-field operation reduces the effect of particle trajectories with kinetic energies below 200 MeV, while room-temperature operation mitigates radiation damage through the spontaneous repair of unwanted radicals. Recently, we achieved over 60% 1H polarization using a new material, dibenz[a,h]anthracene. The low-field and room-temperature polarized solid target allows impractical experiments with the conventional target system, leading to a next-generation spin-dependent accelerator science.

Speaker: Kenichiro Tateishi (RIKEN)

SPIN2025_tateishi.pdf

28 New concept of general-purpose spectrometer with proton polarimeter function

we propose a novel approach to measure the final-state proton polarization in large-acceptance collider experiments. Using existing tracking devices and supporting structure material, general-purpose spectrometers can be utilized as a large-acceptance polarimeter without hardware upgrade. This approach is tested at BESIII, and can be applied at nearly all major facilities, such as Belle-II, CMS, ATLAS, LHCb, CBM, EIC etc., enabling general-purpose spectrometer to extract final-state proton polarization in addition to the traditional four-momentum measurements. This capability would vastly expand the physics reach of these experiments, and has potential for substantial impact across nuclear and particle physics.

Speaker: Yutie Liang (Institute of Modern Physics, CAS)

henp_v6_upload.pdf

29 Spin manipulation in atomic and molecular systems for nuclear spin applications

Nuclear spin polarization has important applications across various fields, including physics and medicine. It also offers several advantages, such as cross-section enhancement, in the five-nucleon fusion reactions, namely the D-T and D-$^3$He reactions. This work presents a theoretical study of spin dynamics in the hyperfine regime for selected atomic and molecular systems and explores alternative techniques to generate or enhance nuclear spin polarization in these systems. Particular emphasis is placed on coherent spin manipulation strategies and the role of hyperfine interactions in transferring angular momentum from electronic (in atoms) or rotational (in molecules) to nuclear degrees of freedom.

Speaker: Chrysovalantis Kannis (Heinrich-Heine-Universität Düsseldorf)

spin2025_kannis1.pdf

spin2025_kannis1.pptx

10:10 Coffee/Tea break

30 Development of Polarized 3He at CSNS

The development of polarized neutron technology is pivotal for advancing studies in material science and fundamental physics, particularly in probing magnetic structures and symmetry violations. At the China Spallation Neutron Source (CSNS), significant progress has been made in the design and implementation of polarized 3He neutron spin filters (NSFs) based on spin-exchange optical pumping (SEOP) [1-5]. An off-situ system demonstrated exceptional performance with 77.4% 3He polarization and a polarization lifetime exceeding 200 hours, making it highly suitable for long-duration experiments [2]. The in-situ NSFs also achieve significant progress, building on the first-generation (70 cm × 70 cm × 60 cm, 74.4% ³He polarization) [3], a compact in-situ system (55 cm × 56 cm × 48 cm) was developed [4], integrating a uniform magnetic field (<1.74×10⁻⁴/cm), dual-laser optical pumping, and precise thermal control (±0.15°C) with low-noise NMR monitoring. Validated on the BL-20 beamline, this system achieved 75.66%±0.09% 3He polarization and 96.30% neutron polarization at 2 Å. These advancements have enabled versatile deployment across multiple CSNS beamlines. For instance, the Back-n white neutron source utilizes the in-situ NSF for time-reversal violation studies [5], while a specially designed in-situ NSF for the Very Small Angle Neutron Scattering (VSANS) instrument successfully implemented China’s first polarization-analyzed small-angle neutron scattering (PASANS) technique [6].

As an underdevelopment polarized neutron facility, our group poised to enhance system stability and expand the applications in complex magnetic materials with polarized neutron, such as investigations of magnetic skyrmions and beyond-Standard Model physics. Future efforts will focus on optimizing performance for advanced experiments in nuclear weak interactions and exotic symmetry-breaking phenomena.

[1] Zecong Qin, Chuyi Huang, Z. N. Buck et al., Development of a 3He Gas Filling Station at the China Spallation Neutron Source, CHIN. PHYS. LETT., 38, 5 (2021) 052801.
[2] Chuyi Huang, Junpei Zhang, Fan Ye, et al., Development of a Spin-Exchange Optical Pumping-Based Polarized 3He System at the China Spallation Neutron Source (CSNS), CHIN. PHYS. LETT., 38, 9 (2021) 092801.
[3] Zhang, J., Huang, C., Qin, Z. et al. In-situ optical pumping for polarizing 3He neutron spin filters at the China Spallation Neutron Source. Sci. China Phys. Mech. Astron., 65, 241011 (2022).
[4] Jian Tang, Bin Wang, Chuyi Huang et al., A compact in-situ polarized 3He system for neutron scattering[J]. Chin. Phys. Lett., 42(2): 022901 (2025).
[5] M. Zhang, Z. Yang, J. Zhang et al., First use of a polarized 3He neutron spin filter on the back-n white neutron source of CSNS, Nuclear Inst. and Methods in Physics Research, A, 1072, 170184 (2025).
[6] Long Tian, Han Gao, Tianhao Wang et al., Polarization-Analyzed Small-Angle Neutron Scattering with an in-situ 3He neutron spin filter at the China Spallation Neutron Source, arXiv:2501.13647 https://doi.org/10.48550/arXiv.2501.13647.

Speaker: Junpei 张俊佩 (高能所)

01_Development of Polarized 3He at CSNS for SPIN.pptx

31 \bf{PREFER} (\bf{P}olarization for \bf{F}usion \bf{E}xperiments and \bf{R}eactors: what is moving around the fusion with polarized fuel?

The PREFER (Polarization REsearch for Fusion Experiments and Reactors) collaboration aims to address the know-hows in different fields and techniques to the challenging bet on energy production by nuclear fusion with polarized fuel. The collaboration involves different institutions and researchers, sharing skills and peculiar abilities, having then possibilities to span over a variety of tasks and objectives, which are under the responsibility of the authors of this contribution, leading their groups.
The collaborators, each in their own activities, starting from facing open questions in the fusion reaction physics, already reach promising results, which have also acted as an inspiration and stimulus for other groups and investigations.
In the following we will report in the present status of the collaboration results and working plans, opening a window on what is being moved around.

Speaker: Prof. Giuseppe Ciullo (INFN-Ferrara and Dipartimento di Fisica e SdT dell'Università di Ferrara)

2025_SPIN_PREFER_Ciullo.pdf

2025_SPIN_PREFER_Ciullo.pptx

32 Spin-Polarized Proton-Boron (p-¹¹B) Fusion: Pathways to Clean Energy

Proton-boron (p-¹¹B) fusion is widely recognized as a promising candidate for future clean energy due to its advantages of abundant fuel, inherent safety, and minimal neutron emissions. However, the practical realization of p-¹¹B fusion faces significant challenges, primarily due to its stringent ignition conditions and relatively low reaction cross-section. Recently, spin polarization has emerged as a potential method to enhance the reaction rate and improve the feasibility of p-¹¹B fusion. This presentation reviews the current status and recent progress in p-¹¹B fusion research, emphasizing the role of spin-polarized fuel in improving reaction efficiency, and discussing the innovative approaches proposed by ENN Energy Research Institute using spherical torus (ST). Additionally, we highlight theoretical and experimental studies on spin-polarized p-¹¹B fusion, including cross-section measurements, fuel (especially boron) preparation, plasma generation and sustainment. The synergy between advanced magnetic confinement configurations, such as ST, and spin-polarized fuel is identified as a promising pathway toward commercial fusion energy. Finally, we outline future research directions and collaborative opportunities within the spin-polarization physics community to accelerate the development of p-¹¹B fusion as a viable energy source.

Speaker: Dr Zhi Li

20250922-SPIN-ZHI.pptx

33 Effects of Spin Polarization on the Proton-Boron Reaction

In the selection of fusion fuels, proton and boron-11 as an ideal choice for commercialization due to its abundant raw materials and the absence of neutron production in the reaction. Compared with other fusion fuels, the proton-boron reaction has a smaller cross-section and requires a higher ignition temperature. To address or mitigate the impact of these difficulties, it is necessary to explore methods to enhance the nuclear reaction cross-section or improve the heating efficiency of the reaction products. Since the nuclei used in fusion reactions possess non-zero intrinsic spin angular momentum, the different spin orientations of the reactants can change the cross-section due to the constraints of angular momentum conservation. This presentation begins by discussing the advantages of selecting proton-boron as a candidate in the magnetic confinement fusion, as well as the challenges we will encounter during its application. To realize the proton-boron fusion reaction, we list several methods that could be employed to reduce the ignition requirements required for proton-boron reactions. Nuclear spin polarization as a potential method, which is considered in the report and the influence of nuclear spin orientation on the cross-section is also explored.

Speaker: Wei Yang (新奥科技发展有限公司)

04_yangwei-effects of spin polarization on the proton-boron reaction.pptx

Fundamental symmetries and spin physics beyond the standard model: 02

Conveners: Xu Feng

Conveners: Bin Yan (IHEP) , Peng Sun (IMP, CAS)

34 Search for CP violation with spin entangled hyperon-antihyperon pairs at BESIII

With the largest datasets on $e^+ e^-$ annihilation at the $J/\psi$ and $\psi(3686)$ resonances collected at the BESIII experiment, multi-dimensional analyses making use of spin polarization and entanglement can shed new light on the production and decay properties of hyperon-antihyperon pairs. In a series of recent studies performed at BESIII, significant transverse spin polarization of the (anti)hyperons has been observed in $J/\psi$ and $\psi(3686)$ to $\Lambda \bar{\Lambda}$, $\Sigma\bar{\Sigma}$, and $\Xi\bar{\Xi}$. For the first time, the decay asymmetry parameters of hyperons and antihyperons have been determined independently with high precision. Comparing the hyperon and antihyperon decay parameters provides precise tests of direct $\Delta S=1$ CP-violation, complementing the studies performed in the kaon sector. Additionally, BESIII investigates weak radiative hyperon decays, semi-leptonic hyperon decays, and hyperon-nucleon interactions.

Speaker: Dr Hong-Fei Shen (IHEP)

Hyperon_CPV_BESIII_SPIN205.pdf

35 extremely strong evidence of CPV in baryon-anti-baryon production processes of heavy hadron decays

The violation of the charge-parity (CP) transformation symmetry, which although has been observed in plenty of pure meson decay processes, was only confirmed just very recently by the LHCb collaboration in the four-body decay of the heavy baryon $\Lambda_b^0$, $\Lambda_b^0\to p K^- \pi^+ \pi ^-$, through a comparison of the decay branching ratio with that of the CP-conjugate process. However, the detailed dynamics behind this CP asymmetry is obviously far from clear. In this talk, we propose a formalism for the full analysis of the decay angular correlations in four-body cascade decays of heavy hadrons which can provide more information about the CP violation in these decays.
To illustrate this, we apply the decay angular correlation analysis of CP violation to another four-body decay channel that involve baryons, $B^0\to p\bar{p}K^+\pi^-$, which has also been investigated by the LHCb collaboration with no evidence of CP violation being found. Surprisingly, with the event yield extracted inversely from the published data of LHCb, we obtain non-zero CP asymmetries of about $10\%$ corresponding to the decay angular correlations at larger than $5\sigma$ confidence level, which are considerably larger than the CPA asymmetries observed in the $\Lambda_b^0\to p K^- \pi^+ \pi ^-$ channel, indicating that CP violation could have been observed in processes involving baryons much earlier if the full analysis of angular correlations had been performed. We suggest our experimental colleagues to perform full decay angular correlation analyses of CP violation in four-body decays of heavy hadrons, including the above two decay channels.

Speaker: Prof. Zhen-Hua（振华） Zhang（张） (University of South China)

4bodyCPA.pdf

36 Bell Inequality Violation of Light Quarks in Dihadron Pair Production at Lepton Colliders

Spin correlations between particles produced at colliders provide valuable insights for quantum information studies. While traditional studies of quantum information at colliders are typically limited to massive particles with perturbative decay, we propose an innovative method to explore the Bell inequality in massless quark pair systems by analyzing the azimuthal correlations in $\pi^+\pi^-$ dihadron pair production at lepton colliders. Revisiting the Belle data, we have shown the potential to detect Bell inequality violation of light quarks by introducing an additional angular cut, achieving a significance of 2.5 $\sigma$ even in the worst-case scenario of 100\% correlated systematic uncertainties in each bins. The significance substantially exceeds $5\sigma$ when considering uncorrelated systematic uncertainties. Our approach opens avenues for exploring spin quantum information with non-perturbative processes as spin analyzer and leverages existing data for quantum information research.

Speaker: Prof. Bin Yan (IHEP)

QE_quarks_Spin2025.pdf

37 Transverse spin effects and light-quark dipole moments at colliders

We propose a novel series of methods to investigate light-quark dipole interactions at colliders. These methods include: (1) utilizing the azimuthal asymmetry of a collinear dihadron pair $(h_1h_2)$ produced in association with an additional hadron $h'$ at lepton colliders; (2) examining the azimuthal asymmetries of a collinear dihadron in semi-inclusive deep inelastic lepton scattering off an unpolarized proton target at the Electron-Ion Collider. These asymmetries provide a unique means to observe transversely polarized quarks, which arise from quantum interference in the quark spin space, and are exclusively sensitive to dipole interactions at the leading power of the new physics scale. Consequently, they exhibit a linear dependence on the dipole couplings, free from contamination by other new physics effects. This approach has the potential to significantly strengthen current constraints by one to two orders of magnitude. By combining all possible channels of $h'$, this novel approach enables the disentanglement of the up and down quark dipole moments. Additionally, by controlling the center-of-mass energy and the electron’s longitudinal polarization, it separates the contributions of photon and weak boson. Furthermore, it allows for a simultaneous determination of both the real and imaginary parts of the dipole couplings, offering a new avenue for investigating potential $CP$-violating effects at high energies.

Speaker: Xinkai Wen (Peking University)

dihadron_dipole_BhungSingKai.pdf

10:00 Coffee/Tea break

38 The Search for Electric Dipole Moments of Charged Particles in Storage Rings

The dominance of matter over antimatter in the universe remains one of the key unresolved questions in modern physics. According to the Sakharov conditions, this asymmetry requires a violation of CP symmetry. While the Standard Model includes CP-violating effects, they are insufficient to account for the observed imbalance. A promising candidate for additional sources of CP violation is the permanent Electric Dipole Moment (EDM) of particles. The Standard Model predicts extremely small EDMs, while many theories beyond the Standard Model suggest values within experimental reach. To date, all measurements of EDMs have been consistent with zero, providing stringent upper limits on the EDM of various particles.

EDMs must align with a particles' spin, allowing their detection through changes in spin polarization in electric fields. Storage rings are ideal for measuring the EDMs of charged particles, such as the deuteron, for which no experimental limit currently exists. During this talk, I will present the results of the first direct measurement of the deuteron EDM at the Cooler Synchrotron COSY.

Speaker: Achim Andres (FZJ / GSI)

20250917_SPIN2025.pdf

20250923_SPIN2025.pdf

39 Linearly Polarized Photon Fusion as a Precision Probe of the Tau Lepton Dipole Moments at Lepton Colliders

We present a comprehensive investigation into the anomalous magnetic dipole moment ($a_\tau$) and electric dipole moment ($d_\tau$) of the $\tau$ lepton using the $\gamma\gamma \to \tau^+\tau^-$ process at future lepton colliders, with the Super Tau-Charm Facility serving as a benchmark. By employing transverse-momentum-dependent factorization, we introduce novel observables derived from $\cos2\phi$, $\sin2\phi$, and $\cos4\phi$ azimuthal asymmetries to precisely probe the $\tau$ lepton's electromagnetic structure. Our analysis significantly enhances the precision of $a_\tau$ constraints within the photon-photon fusion process, yielding $\mathrm{Re}(a_\tau) \in [-4.5, 6.9] \times 10^{-3}$ at the $2\sigma$ confidence level, which approaches the precision of the Standard Model prediction. These findings highlight the considerable potential of azimuthal asymmetry measurements for high-precision determinations of fundamental particle properties at future lepton colliders.

Speaker: Fang Xu (复旦大学)

SPIN2025_Fang Xu_Fudan University.pdf

40 SEARCH FOR TIME-INVARIANCE VIOLATION IN DOUBLE POLARIZED pd-, 3He-d and dd-SCATTERING AND TEST OF THE pN SPIN AMPLITUDES AT HIGH ENERGIES

The total cross section of the interaction of transversaly polarized ($P_y$) proton ($^3$He or deuteron) with the tenzor polarized ($P_{xz}$) deuteron constitues a null-test signal of time-reversal invariance violation under parity conservation (TVPC) in such processes (see Ref. [1] and references therein). This result follows from the optical theorem providing this signal for such kind of double polarized scattering, as a product of unknown constant of the TVPC interaction and the ordinary T-even spin flip helicity $\phi_5$ amplitude of pN-scattering and the deuteron form factor. Knowledge of energy dependence of this signal is necessary for planning experiments and this function was calculated (up to unknown TVPC constant) for pd [1] in the GeV region and recently at energies of SPD NICA for pd [2], $^3$He-d [3] and dd [4] collisions.
Since some of hadronic spin amplitudes of pN elastic scattering are absolutely necessary for search of time-invariance violation in polarization experiments, it is important to have a test of existing parametrizations of these and others spin pN amplitudes especially at high energies where data are non-complete and, therefore, some model parametrizations for pN amplitudes are used [5,6]. As known, spin observables of the pd-elastic scattering in the GeV region are well described on the basis of the spin-dependent Glauber theory [7] using data on spin amplitudes of elastic pp- and pn-scattering. Therefore, spin observables of pd-elastic scattering being analyzed within the Glauber theory can be used as an effective test of existing spin pN-amplitudes. At the NICA SPD collider the asymmetric pd-collision mode will be not implemented, while the symmetric dd-mode will be realized. We show [8] that vector and tenzor analyzing powers $A^p_y$, $A_y^d$, $A_{yy}$, and spin-correlations coefficients $ С_{y,y}$, $C_{yy,y}$ of the dd→ npd reaction for the pole mechanism with a subprocess of quasi-free pd-elastic scattering are directly related to the corresponding spin observables of the free pd- elastic scattering. Most of these observables a very sensitive to the spin pN amplitudes. Therefore measurement of these observables in the reaction dd-npd at SPD NICA in kinematics of quasi free pd-pd process and forthcoming analysis within the Glauber theory will be important as an effective test of available spin pN-amplitudes.

[1] Yu.N. Uzikov, A.A. Temerbayev, Phys. Rev. C 92 (2015) 1, 014002
[2] Yu. N. Uzikov, M.P. Platonova, Phys. Part. Nucl. 56, No. 2, (2025) 533.
[3] Yu.N. Uzikov, M.N.Platonova, JETP Lett. 118 (2023) 11, 785.
[4] M.N. Platonova, Yu.N. Uzikov, Chin.Phys.C 49 (2025) 3, 034108.
[5] A. Sibirtsev, J. Haidenbauer, S. Krewald, U.-G.Meissner, Eur. Phys. J. A 45 (2010) 357.
[6] O.V. Selyugin, Phys.Rev. D 110 (2024) 11, 114028 ; e-Print: 2407.01311 [hep-ph].
[7] M.N. Platonova, V.I. Kukulin, Phys.Rev. C 81 (2010) 014004, Phys.Rev.C 94 (2016) 6, 069902; (erratum); Eur.Phys.J.A 56 (2020) 5, 132.
[8] Yu. N. Uzikov, e-Print: 2506.17799 [nucl-th]

Speaker: Yuriy Uzikov (Joint Institute for Nuclear Researche)

SPIN-2025-Qingdao.pdf

41 A new experimental proposal to search for T-violating μ^+ polarization in K^+→π^0 μ^+ ν decay using stopped positive kaons at J-PARC

Time reversal symmetry has long been a subject of interest from pre-modern physics time, since it implies the reversibility of motion. In the K^+→π^0 μ^+ ν (K_μ3) decay, the transverse muon polarization (P_T) is defined as the polarization component perpendicular to the decay plane. A non-vanishing value of P_T provides clear evidence for T-violation under the condition that spurious effects from final state interactions are negligibly small. We are now proposing a new T-violation experiment to achieve ΔP_T~10^(-5) at the J-PARC Hadron Hall without using a magnetic spectrometer. The most important characteristic of the new experiment is the measurements of the muon momentum vector, the π^0 momentum vector, and the muon polarization by the same highly segmented sequential electro-magnetic calorimeter surrounding the K^+ stopping target. Here it should be noted that one of key issues in the experiment is the choice of a scintillation material which can preserve the muon spin polarization for a reasonably long time [1].
A test experiment to measure residual muon polarization in CeF3, LaF3, PrF3, and NdF3 scintillating crystals was performed using a 100% polarized muon beam at J-PARC MLF. In the longitudinal field of 140 Gauss, the muon polarization in these materials was obtained to be 90% at room temperature, which is high enough to perform the new T-violation experiment [1-3]. Since the calorimeter should be placed very close to the K^+ beam line, a single rate for each module will be very high and the timing resolution should be better than 1 ns to reduce accidental background effects. The timing resolution using a CeF3 crystal with the size of 20×20×20 mm^3 was obtained to be ~100 ps using solar-blind phototubes. The time interval of the two CeF3 detector signals generated by the cosmic ray passage was measured. The timing resolution is sufficiently good, and the accidental backgrounds must be harmless in the proposed T-violation experiment.
The μ^+ polarization can be determined by the delayed e^+ signals from the μ^+ decay detected by the calorimeter module around the muon stop. The experimental method to measure the e^+ asymmetry determination by selecting the π^0-forward and backward events is adopted to suppress systematic uncertainties. Furthermore, the analyzing power in the polarization measurement should be improved by measuring the e^+ energy using the calorimeter [3] because the magnitude of the e^+ asymmetry depends on the e^+ energy, while only the energy　integrated asymmetry is obtained in the standard polarization measurement. The dedicated analysis method has been developed by separating events into partial energy regions and optimizing weight parameters to averaging the e^+ asymmetry in each bin.
In this talk, some details of the future T-violation experiment, the results of the test experiment to determine the residual polarization in CeF3, LaF3, PrF3, and NdF3 materials, the timing resolution of the CeF3 detector, and an increase in the analyzing power in the polarization measurement will be reported.

References
[1] S. Shimizu et al., Nucl. Instrum. Methods A 945 (2019) 162587.
[2] K. Horie et al., Nucl. Instrum. Methods A 1037 (2022) 166932.
[3] Horie et al., Nucl. Instrum. Methods A 1066 (2024) 169606.

Speaker: Prof. Suguru Shimizu (The University of Osaka)

spin2025_shimizu.pdf

42 Toward the first experiments of T-violation search in neutron-induced compound nuclear reaction

The CP violation beyond the standard model is not only physically interesting on its own, but also a key for understanding the baryon asymmetry in the current universe. In a low energy region, instead of directly probing it, many efforts to search the violation of time-reversal symmetry(T-violation) continue in various physics systems with high sensitivity. Among those, neutron-induced compound nuclear reactions are interesting because the enhancement of parity-nonconservation effect(PNC) has been found in many compound nuclear states. Particularly, in the neutron resonant absorption in Lanthernum nuclei(La) at 0.75eV, the enhancement is so great that it reaches 10^6. This enhancement for the PNC can be also expected for the T-violation from recent experimental results and theoretical calculations. Additionally, this system is sensitive to a different physical parameter indicating the magnitude of the T-violation from the neutron EDM, so that it is also attractive in terms of a different search region. Thus, the NOPTREX collaboration is planning the T-violation search with La targets as a first attempt. One big issue is the development of a polarized La target because polarized targets except for proton and deuteron have not been realized yet as a practical use. In this presentation, we will introduce the overview of the first stage of the T-violation experiment, Phase-I, and report current status in the NOPTREX project.

Speaker: Masataka Iinuma (Hiroshima University, AdSE)

9_Spin2025_iinuma_Hiroshima_University.pdf

Nucleon helicity structure: 01

Conveners: Matthew Posik, Raza Sabbir Sufian, Jinlong Zhang

Conveners: Emanuele Roberto Nocera (Università degli Studi di Torino and INFN Torino) , Stephen Pate (New Mexico State University)

43 Helicity Dependent Distribution Functions of the proton and Λ and Σ0 Baryons

Using continuum Schwinger function methods, a coherent set of predictions for proton, Λ and Σ0 baryons is delivered - both helicity dependent and unpolarised. The analysis reveals impacts of diquark correlations and SU(3)-flavour symmetry breaking, some of which are significant. For instance, were it not for the presence of axialvector diquarks in the Σ0, the strange quark could carry none of the Σ0 spin. The discussion will canvass issues that include helicity retention in hard scattering processes; the sign and size of polarised gluon DFs; and the origin and decomposition of baryon spins.

Speaker: Craig Roberts (Nanjing University)

2509_Spin2025_RobertsCD.pptx

44 Progress on Constraining the Strange Quark Contribution to the Nucleon Spin

We report on a global fit of neutral-current elastic (NCE) neutrino-scattering data and parity-violating electron-scattering (PVES) data with the goal of determining the strange quark contribution to the vector and axial form factors of the proton. Knowledge of the strangeness contribution to the axial form factor, $G_A^s(Q^2)$, at low $Q^2$ will reveal the strange quark contribution to the nucleon spin, as $G_A^s(Q^2=0)=\Delta s$. Previous fits [1,2] of this form included data from a variety of PVES experiments (PVA4, HAPPEx, G0, SAMPLE) and the NCE neutrino and anti-neutrino data from BNL E734. These fits did not constrain $G_A^s(Q^2)$ at low $Q^2$ very well because there was no NCE data for $Q^2<0.45$ GeV$^2$. Our new fit includes for the first time MiniBooNE NCE data from both neutrino and anti-neutrino scattering; this experiment used a hydrocarbon target and so a model of the neutrino interaction with the carbon nucleus was required. Three different nuclear models have been employed; a relativistic Fermi gas (RFG) model, the SuperScaling Approximation (SuSA) model, and a spectral function (SF) model [3]. We find a tremendous improvement in the constraint of $G_A^s(Q^2)$ at low $Q^2$ compared to previous work, although more data is needed from NCE measurements that focus on exclusive single-proton final states, for example from MicroBooNE [4]. This work has been published in Physical Review D [5].
[1] S.F. Pate, D. McKee, V. Papavassiliou, Phys. Rev. C78, 015207 (2008)
[2] S.F. Pate, D. Trujillo, EPJ Web of Conferences 66, 06018 (2014)
[3] C. Giusti and M.V. Ivanov, J. Phys. G: Nucl. Part. Phys. 47 024001 (2020)
[4] L. Ren, NuFact 2021, PoS, 402, 205 (2022), 10.22323/1.402.0205
[5] S.F. Pate et al., Phys. Rev. D 109, 093001, 2024

Speaker: Stephen Pate (New Mexico State University)

SPIN2025_Pate.pdf

45 Recent progress on inclusive quarkonium production and polarization

Quarkonium production and polarization serves as a vital testing ground for quantum chromodynamics (QCD), offering critical insights into both perturbative and nonperturbative dynamics. In the nonrelativistic QCD (NRQCD) factorization framework, inclusive production cross sections of quarkonia are expressed as products of perturbatively calculable short-distance coefficients (SDCs) and nonperturbative long-distance matrix elements (LDMEs), which are hypothesized to be universal across production processes. For three decades, the validation of LDME universality has been central to understanding quarkonium production mechanisms. However, different groups extracted dramatically different sets of the three color-octet LDMEs of J/\psi, and none of them can describe all the production and polarization data from LHC, HERA, LEP and Belle, challenging the universality of LDMEs. In this talk, we will report our recent progress on factorizing the LDMEs into products of wave functions and gluonic correlators based on the potential NRQCD (pNRQCD) effective theory and comprehensive phenomenogical study on inclusive quarkonium prduction and polarization. We show that most of the data can be well described in the framwork of NRQCD factorization and those still evade a consistent discription coincide with “extenstions” of endpoint regions.

Speakers: Xiangpeng Wang (CCNU) , 翔鹏 王 (华中师范大学)

talk_XPWang.pdf

46 Perspective on proton polarised parton distribution functions

Supposing there exists an effective charge which defines an evolution scheme for both unpolarised and polarised parton distribution functions (DFs) that is all-orders exact and using Ansätze for hadron-scale proton polarised valence quark DFs, constrained by flavour-separated axial charges and insights from perturbative quantum chromodynamics, predictions are delivered for all proton polarised DFs. The pointwise behaviour of the predicted DFs and, consequently, their moments, compare favourably with results inferred from data.

Speaker: Dr Peng Cheng (Anhui Normal University)

SPIN2025-pchengv2.pptx

09:55 coffee break

47 Nucleon gluon PDF from lattice QCD

The unpolarized and polarized gluon parton distribution functions are calculated in lattice QCD using the Large-Momentum Effective Theory(LaMET) method. The calculations are carried out at three different lattice spacings and pion mass around 300MeV. The results are extrapolated to the continuum and infinite momentum limits. The unpolarized gluon PDF is consistent with the global fit of CT18NNLO.

Speaker: Liuming Liu (Institute of Modern Physics, CAS)

talk_LiumingLIu.pdf

48 Total Gluon Helicity from Lattice

We use the ensemble C24P29 provided by the CLQCD collaboration, insert the topological current using the proton external state of the momentum smear under the Coulomb gauge of the 5-HYP smear, extract the matrix elements to calculate the gluon helicity under lattice QCD, and the calculation proves that different components of the topological currents ($K^z$ and $K^t$) can be used to give consistent results within the error range. In addition, we use the RI/MOM renormalization scheme, consider the mixing of gluon and quark helicity, and extract the renormalization constant to give the gluon helicity result under $\overline{\mathrm{MS}}$ scheme.

Speaker: Dian-Jun Zhao (CUHK(Shenzhen))

Dian-Jun Zhao Spin2025.pdf

49 High-Precision Determination of Quark Spin in Lattice QCD: A Novel Method

We propose a ``blending" algorithm that projects the all-to-all fermion propagator onto spatial low-frequency modes (LFM) combined with a stochastic estimate of spatial high-frequency modes (SHFM) at each time slice.
This approach enables the calculation of arbitrary-point correlation functions for arbitrary hadron states in strongly interacting quantum field theories (QFT) with fermions, such as quantum chromodynamics (QCD).
Specifically, LFM allows the construction of spatially extended hadron states below a certain energy threshold by diagonalizing multi-fermion interpolation fields. Meanwhile, the local interactions required for N-point correlation functions in QFT can be approximated in an unbiased manner through a reweighted summation of both LFM and SHFM contributions.
To demonstrate the efficiency of this algorithm, we obtained {\color{black} $g_A^u=0.895(15)$, $g_A^d=-0.338(15)$, $g_A^s=-0.0245(72)$, $g_A^{u+d+s}=0.533(28)$ and $g_A^{u-d}=1.2339(43)$ } for nucleon at $m_{\pi}=300$ MeV and $a=0.077$ fm using 40 configurations.
The consistency check of the pion electric form factor and charge radius derived from 3-point and 4-point correlation functions is also provided.

Speaker: Zhicheng Hu (Chinese Academy of Sciences Institute of Modern Physics)

Zhicheng_QuarkSpin4Octet_Spin(2025).pdf

50 Pion and kaon fragmentation functions from continuum Schwinger function methods

Using continuum Schwinger function methods and the Drell-Levy-Yan relation, this work provides a unified description for pion and kaon distribution functions and fragmentation functions (FFs). After evolution to higher scale, the obtained FFs conform with a range of physical expectations for FF behaviour on the endpoint domains, such as that nonsignlet FFs vanish at z=0 and singlet FFs diverge faster than 1/z. These FFs are compared with the existing experimental fits, and the comparison provides meaningful insights into the behavior of FFs. Predictions for hadron multiplicities in jets are also delivered. They reveal SU(3) symmetry breaking in the charged-kaon/neutral-kaon multiplicity ratio, whose size diminishes with increasing reaction energy.

Speaker: Hui-Yu Xing (Nanjing University)

Huiyu Xing-FF.pdf

51 Fragmentation Functions of Charged Hadrons at NNLO and Constraints on the Proton PDFs

We present the first global analysis of fragmentation functions (FFs) for light charged hadrons ($\pi^\pm, K^\pm$) at full next-to-next-to-leading order in QCD, incorporating world data from both single-inclusive electron-positron annihilation and semi-inclusive deep-inelastic scattering. The collinear factorization has been tested with low-momentum-transfer data and has demonstrated success at high hadron momenta. Additionally, we study the impact of current global data on hadron production to the parton distribution functions (PDFs), and find they favor a reduced asymmetry in the strange (anti)quark PDFs, as compared to the asymmetry predicted by state-of-the-art PDFs derived from inclusive data.

Speaker: Dr XiaoMin Shen (Institute of Modern Physics (IMP), CAS)

spin2025-0923-shen.pdf

Spin in heavy ion collisions: 02

Conveners: Enrico Speranza, Jinhui Chen, Takafumi Niida

Conveners: Francesco Becattini (Università di Firenze) , Xiaozhi Bai (University of Science and Technology of China)

52 A solvable model for spin polarizations with flow-momentum correspondence

We present an analytically solvable model based on the blast-wave picture of heavy-ion collisions with flow-momentum correspondence. It can describe the key features of spin polarizations in heavy-ion collisions. With the analytical solution, we can clearly show that the spin polarization with respect to the reaction plane is governed by the directed flow, while the spin polarization along the beam direction is governed by the ellipticity in flow and in transverse emission area. We also give an analytical expression for the last component of the spin polarization 𝑃𝑥 the in-plane polarization, in heavy-ion collisions that has, to our knowledge, not been discussed in theories nor measured in heavy-ion collision experiments. The prediction of 𝑃𝑥 can be tested in experiments and will contribute to provide a complete and consistent picture of spin phenomena in heavy-ion collisions.

Speaker: Qun Wang (University of Science and Technology of China)

QunWang_spin-2025-1.pdf

53 Spin polarization from hadrons to (anti-)(hyper-)nuclei in high-energy nuclear collisions

Particles of non-zero spin produced in non-central heavy-ion collisions are expected to be polarized along the direction perpendicular to the reaction plane because of their spin-orbit interactions in the produced matter. In this talk, I will show that the hypertriton, which is the lightest hypernucleus, is also polarized in these collisions. I will demonstrate that the polarization and decay pattern of hypertriton provides a unique tool to decipher the spin structure of hypertriton wavefunction. I will further discuss the possibility of studying the spin correlations among nucleons and Λ hyperons in the produced hadronic matter from the measured Λ polarization in non-central heavy-ion collisions.

Reference: Kai-Jia Sun et al., Phys. Rev. Lett. 134. 022301 (2025)

Speaker: KaiJia Sun (Institute of Modern Physics, Fudan University)

HypernucleiPolarization-kjsun-FDU.pdf

54 Holographic spin alignment of vector mesons in magnetized plasma

We establish a holographic framework for investigating spin alignment (ρ₀₀) of flavorless vector mesons using gauge/gravity duality. By analyzing dilepton production via meson decay, we derive a universal relation between production rates per spin channel and the in-medium spectral function—computable holographically for strongly coupled systems. Applying this to J/ψ and ϕ mesons in a moving thermal bath via the soft-wall model, we find starkly contrasting behaviors at T = 150 MeV: J/ψ spectral functions exhibit sharp resonance peaks, signaling quasi-stable c̄c bound states; ϕ mesons show no resonant structures, indicating melted s̄s pairs. Under an instantaneous freeze-out assumption, we map these spectral functions to free-streaming observables by projecting onto states near the vacuum meson mass. This reveals: J/ψ: ρ₀₀ > 1/3 (positive deviation) in the helicity frame; ϕ: ρ₀₀ < 1/3 (negative deviation), implying distinct global spin-alignment properties. Further analysis of J/ψ spin parameters (λ_θ, λ_φ, λ_{θφ}) demonstrates their sensitivity to magnetic fields, momentum, and temperature—providing quantitative insights into QCD medium effects.
Moreover, we apply our model to real heavy-ion collisions for three different spin quantization directions. Further comparisons with experimental data show qualitative agreement for spin parameters in the helicity and Collins-Soper frames.

Speaker: Defu Hou (CCNU)

DefuHou_spin alignment-0918n.pdf

55 Global quark spin correlations in relativistic heavy ion collisions

Measurements by the STAR Collaboration of global Λ hyperon polarization and 𝜙,𝐾∗0 meson spin alignment in heavy-ion collisions [1, 2] have confirmed the global polarization of quark matter [3, 4] and indicated strong quark–antiquark spin correlations. Quark spin correlations have emerged as a new frontier and a rapidly developing research hotspot.

In Ref. [5], we propose a systematic method to describe quark spin correlations in quark matter, classifying them into local and long-range correlations. We show that the effective quark correlations contain genuine spin correlations originating directly from the dynamical process as well as those induced by averaging other degrees of freedom. We present a comprehensive study of the global polarization and spin correlations of vector mesons, spin-1/2 and spin-3/2 baryons, and baryon–(anti)baryon pairs in heavy-ion collisions [6]. This talk will summarize the main ideas and results [5, 6] and discuss future prospects.

References
[1] L. Adamczyk et al. [STAR], “Global Λ hyperon polarization in nuclear collisions: evidence for the most vortical fluid,” Nature 548, 62 (2017).
[2] M. S. Abdallah et al. [STAR], “Pattern of global spin alignment of 𝜙 and 𝐾∗0 mesons in heavy-ion collisions,” Nature 614, 244 (2023).
[3] Z. T. Liang and X. N. Wang, “Globally polarized quark-gluon plasma in non-central A+A collisions,” Phys. Rev. Lett. 94, 102301 (2005).
[4] Z. T. Liang and X. N. Wang, “Spin alignment of vector mesons in non-central A+A collisions,” Phys. Lett. B 629, 20 (2005).
[5] J. p. Lv, Z. h. Yu, Z. t. Liang, Q. Wang and X. N. Wang, “Global quark spin correlations in relativistic heavy ion collisions,” Phys. Rev. D 109, 114003 (2024).
[6] J. p. Lv, Z. h. Yu, Z. t. Liang, “The complete results of global polarization and spin correlation of hadrons with different spins in relativistic heavy ion collisions,” paper in preparation.

Speaker: Ji-peng Lv (Shandong University)

spin2025-jipeng lv.pdf

10:05 Coffee break

56 Longitudinal and global polarization of hyperons in Run 3 Pb-Pb collisions with ALICE

Ultra-relativistic heavy-ion collisions create a hot and dense state of strongly interacting matter — the quark–gluon plasma (QGP). Its space–time evolution is dominated by strong collective expansion, which generates anisotropic flow and demonstrates the nearly perfect fluid nature of the QGP. This anisotropic expansion, in particular the elliptic flow coefficient 𝑣2, gives rise to local shear and vorticities along the beam axis. Through spin–orbit coupling, these vorticities are expected to induce a longitudinal component of hadron polarization. Such measurements provide sensitivity to the early-time dynamics of the collision and constrain key transport properties of the QGP, including its shear and bulk viscosities. A distinct effect, known as global polarization, arises from the very large initial orbital angular momentum present in non-central collisions. This angular momentum is transferred to the medium as its vorticity, resulting in a net alignment of the spins of final-state particles along the global angular momentum direction of the system.

In this talk, I will present new high-statistics results from Run 3 Pb--Pb collisions at 𝑠NN‾‾‾‾√ = 5.36 TeV with the ALICE experiment. These include the more precise measurement of the longitudinal polarization of Λ hyperons at LHC energies, together with the first measurement of longitudinal polarization of Ξ hyperons. In addition, the first observation of global Λ polarization at LHC energies will be reported. These results provide new insight into the rotational structure of the QGP and give insight to the vortical property as well as transport properties of strongly interacting matter under extreme conditions.

Speaker: Prottay Das

1_Spinconf_prottay.pdf

57 Measurements of $\Lambda$, $\Xi$ and $\Omega$ Global Polarization in Au+Au collisions at BES-II energies from RHIC-STAR

The observation of hyperon global polarization along the system's angular momentum has revealed the existence of large vorticities in the medium created by heavy-ion collisions. In this talk, we present measurements of global polarization for $\Lambda$, $\Xi$, and $\Omega$ hyperons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 9.2, 11.5, 14.6, 17.3, 19.6, and 27 GeV, based on high-statistics data collected during the RHIC Beam Energy Scan Phase II (BES-II) with the upgraded STAR detector. The comparison between $\Lambda$ and $\bar{\Lambda}$ polarizations offers potential access to magnetic-field-driven effects. The inclusion of multi-strange hyperons such as $\Xi$ and $\Omega$ introduces additional sensitivity to the later-stage dynamics of the system, placing further constraints on the properties of the QGP and the evolution of its angular momentum. These results provide new insights into the polarization mechanism and the structure of the vorticity fields in heavy-ion collisions.

Speaker: Tong Fu (Shandong University)

Spin2025_Tong_Fu.pdf

58 Spin polarization at relativistic AA and pA collisions

In this talk, we have implemented the quantum kinetic theory combined the relativistic hydrodynamics to study the spin polarization of Lambda hyperons in the relativistic AA and pA collisions. The global polarization can be well described by the current theoretical frameworks. The local polarization in low energies AA collisions and pA collisions cannot be fully understood.

Speaker: Shi Pu (University of Science and Technology of China)

Spin_correlation_SPIN2025_shipu_wide.pdf

59 Determining spin effects in global equilibrium by quantum kinetic theory

In this talk, we will demonstrate how quantum kinetic theory determines spin effects in global equilibrium. We show that by generalizing from constant to varying electromagnetic fields, previously indeterminate spin effects induced by vorticity and electromagnetic fields can now be further pinned down.

Speaker: Jian-Hua Gao (Shandong University at Weihai)

Spin2025-Jianhua Gao.pptx

Lunch

3-dimensional structure of nucleon - TMD

Conveners: Christopher Dilks, Andrea Signori, Ting Lin

Conveners: Alessandro Bacchetta (University of Pavia and INFN) , Dingyu Shao (Fudan University)

60 Application of nuclear covariance matrix in nuclear TMD effects

In this work, we investigate the nuclear modification effects in transverse momentum dependent
(TMD) observables by implementing a nuclear covariance matrix in the treatment of theoretical uncertainties. Global QCD analysis is performed with the aforementioned nuclear covariance matrix to verify its equivalence with the traditional approach of including a nuclear correction parameter. The data analyzed are the Drell-Yan $q_T$-differential data in $pA$ and $\pi A$ collisions. In addition, we also perform global QCD analysis with no treatment for the nuclear effects, verifying the necessity of implementing the nuclear corrections.

Speaker: Yiyu Zhou (University of Turin)

nuclear-TMD-uncertainty-2025-SPIN.pdf

61 Polarized TMD FFs with QCD evolution

The polarized transverse-mementum-dependent fragmentation function (TMD FF) $D_{1T}^\perp$ have attracted lots of attention from both experiment and theory communities. Starting from a isospin symmetric parametrization for $D_{1T}^\perp$, we have studied transverse polarizations of $\Lambda$ in various collisions. Recently we focus on nuclear collisions and study the QGP medium effects via QCD evolution in the impact parameter space. We find that transverse polarization of $\Lambda$ can work as a novel probe of nuclear medium effects in heavy ion collisions.

Speaker: Yu-kun Song (University of Jinan)

songyk-Polarized TMD FFs with QCD evolution.pdf

62 Precision Predictions for Three-Dimensional Nucleon Tomography

We present an analysis of lepton-jet azimuthal decorrelation in deep-inelastic scattering (DIS) at next-to-next-to-next-to-leading logarithmic (N$^{3}$LL) accuracy, combined with fixed-order corrections at $\mathcal{O}(\alpha_s^2)$. In this study, jets are defined in the lab frame using the anti-$k_T$ clustering algorithm and the winner-take-all recombination scheme. The N$^{3}$LL resummation results are derived from the transverse-momentum dependent factorization formula within the soft-collinear effective theory, while the $\mathcal{O}(\alpha_s^2)$ fixed-order matching distribution is calculated using the NLOJET++ event generator. The azimuthal decorrelation between the jet and electron serves as a critical probe of the three-dimensional structure of the nucleon. Our numerical predictions provide a robust framework for precision studies of QCD and the nucleon's internal structure through jet observables in DIS. These results are particularly significant for analyses involving jets in HERA data and the forthcoming electron-ion collider experiments.

Speaker: Shen Fang (Fudan University)

fang spin 2025.pdf

63 qT-slicing with multiple jets at the NNLO and NNLL TMD resummation on dijet production

We present two complementary advances toward precision QCD predictions for multi-jet processes at the LHC, both based on observables constructed with the Winner-Take-All (WTA) recombination scheme. First, we develop two generalizations of the transverse-momentum slicing variable $q_T$ applicable to jet final states, enabling a slicing approach for processes like $pp \to 2$ jets. A proof of concept is provided at NLO, along with factorization formulae that pave the way for NNLO extensions, demonstrated explicitly for $e^+e^- \to 2$ jets. The validation of these $q_T$-like variables crucially relies on the use of WTA axis definition. Second, we perform NNLL resummation for both the $\delta\phi$ and $q_T$ distributions in WTA dijet production, uncovering a novel structure of scale hierarchies in impact-parameter space. We show that large logarithms involving an auxiliary angle $\phi_b$ can be eliminated through refactorization of the soft function and the introduction of additional scale evolution. Together, these developments advance the theoretical toolkit for precision collider phenomenology involving jet observables.

Speaker: Rong-Jun Fu (Fudan University)

qT_slicing_slides.pdf

64 Nucleon Tomography with 0-jettiness

We propose a novel strategy to systematically isolate the nucleon’s intrinsic non-perturbative three-dimensional structure by employing 0-jettiness to suppress initial-state radiation in transverse momentum-dependent (TMD) observables. Applying this method to transverse single spin asymme tries (SSAs) in W$^\pm$ and Z$^0$ boson production at RHIC, we demonstrate a substantial enhancement of the asymmetry signal, enabling a more definitive test of the predicted sign change of the Sivers function–a key prediction of TMD factorization. We further explore its applicability to spin-dependent measurements at the Electron-Ion Collider. Our analysis is formulated within a joint resummation framework that systematically resums large logarithms associated with both the veto scale and the gauge boson’s transverse momentum.

Speaker: Shuo Lin (Shandong University)

shuolin spin3.pdf

15:40 Coffee Break

65 Bjorken x weighted Energy-Energy Correlators from the Target Fragmentation Region to the Current Fragmentation Region

we explore the Bjorken $x$ weighted EEC in DIS from the TFR to CFR. In both regions, a factorization theorem can be derived with SCET, based on which the logarithms can be resummed to all orders in $\alpha_s$. The singular distributions can be derived from the factorized formula, which are compared against the full fixed-order QCD calculations up to NLO. Additionally, we present the resummation results up to NLL in the TFR and N$^3$LL in the TMD region. In the extremely small angle limit, the free hadron gas model is introduced to investigate the non-perturbative distribution. We compared our predictions to partonic $\text{ PYTHIA}$ simulations. Between the hadron gas phase region and the perturbative resummation region, a transition phase is observed. The non-perturbative and hadronization effects in the TMD region were investigated by considering non-perturbative form factors extracted from the semi-inclusive hadron production in DIS. Incorporating these non-perturbative models, we also presented the comparison of our predictions to $\text{PYTHIA}$ simulations.

Speaker: Mr Zihao Mi (Beijing Normal University)

Zihao_SPIN2025.pdf

66 One-Point energy correlator inside jets

In this work, we introduce a new jet observable, the one-point energy correlators (EC), designed to characterize the in-jet energy flow distribution by measuring energy deposition at a specific angle relative to the jet axis. Building upon the transverse momentum dependent physics, we aim for the EC to provide novel insights into jet substructure and offer a new approach to study TMD physics, particularly gluon transverse momentum dependent fragmentation functions (TMDFFs) which are notoriously difficult to extract. We obtain the factorization of the EC jet function within Soft-Collinear Effective Theory and leverage the framework of semi-inclusive TMD fragmenting jet functions. We resum large global logarithms and non-global logarithms (NGLs) and show that the normalized EC jet function exhibits significantly reduced dependence on the factorization scale and is primarily sensitive to the jet scale. Finally, after incorporating non-perturbative effects, we present numerical calculations up to NNLL accuracy for global logarithms and LL accuracy for NGLs, and we compare these predictions with PYTHIA 8 simulations.

Speaker: Zhan Wang

EC_beamer_wz_spin2025.pdf

67 Unveiling the Collins effect in jets with one-point energy correlators

We propose a novel method to probe the Collins effect, a key signature of the nucleon's 3D structure, using an intra-jet energy correlator. This new observable, based on the energy-weighted azimuthal distribution of hadrons within a jet, can be measured in transversely polarized proton-proton collisions at RHIC. The resulting $\sin(\phi_h - \phi_S)$ single-spin asymmetry provides a direct probe of the Collins fragmentation function, offering a new test of its universality and connecting the fields of spin physics and jet substructure. This creates a strong link between the RHIC spin program and future measurements at the Electron-Ion Collider.

Speaker: Wanchen Li (Fudan University)

OPEC_Transversity_SPIN2025_16.9.pdf

68 Fragmentation energy correlators

We initiate a systematic study of fragmentation energy correlators (FECs), which generalize traditional fragmentation functions and encode non-perturbative information about transverse dynamics in parton fragmentation processes.
We define boost-invariant, non-perturbative FECs and derive a corresponding collinear factorization formula. A spin decomposition of the FECs is carried out, analogous to that of transverse-momentum-dependent fragmentation functions.
In this work we focus particularly on the Collins-type quark FEC, which is sensitive to chiral symmetry breaking and characterizes the azimuthal asymmetry in the fragmentation of a transversely polarized quark.

Speaker: Shutao Zhang (Peking University)

FEC_spin.pdf

69 Polarized Energy-Energy Correlators in Jet at STAR

The Energy-Energy Correlators (EEC), initially developed in $e^+e^-$ collisions, provide a powerful method for probing the angular structure of energy flows within jets. In hadronic collisions with transverse polarization, the polarized EEC (pEEC) offers unique sensitivities to parton spin-orbit correlations and spin-dependent transverse-momentum-dependent (TMD) effects. In this presentation, we will present preliminary results of the first measurement of polarized EEC in jets at the STAR experiment, utilizing data from transversely polarized proton-proton ($p^{\uparrow} + p$) collisions at both $\sqrt{s} = 200$ and 510 GeV. This analysis includes both 1-point and 2-point EEC measurements for $\pi^+$ and $\pi^-$ in jets, providing new insights into the spin-dependent dynamics of final state fragmentations.

Speaker: Ting Lin (Shandong University)

SPIN2025_TingLin_20250918.pdf

3-dimensional structure of nucleon: GPD and FF

Conveners: Barbara Pasquini, Sznajder Pawel, Stefan Diehl

Convener: Paweł Sznajder (National Centre for Nuclear Research, Poland)

70 NPS Experiments in Hall C at Jefferson Lab

Deeply Virtual Compton Scattering (DVCS) and exclusive $\pi^0$ electroproduction provide experimental access to Generalized Parton Distributions (GPDs). In these channels, the measured cross sections are expressed in terms of Compton Form Factors (CFFs), which correspond to the first moments of the underlying GPDs. From September 2023 to May 2024, Jefferson Lab Hall C conducted experiment E12-13-010 with a polarized electron beam, utilizing the High Momentum Spectrometer together with the newly commissioned Neutral Particle Spectrometer (NPS) to measure DVCS and exclusive $\pi^0$ cross sections. Data analysis is currently in progress. The full 11 GeV dataset of E12-13-010 covers wide kinematics on an unpolarized proton target and is expected to enable the separation of interference and pure DVCS$^2$ contributions to each Fourier moment through azimuthal, energy, and beam-helicity dependences, along with a systematic Q$^2$ scan of all terms. In parallel, exclusive $\pi^0$ electroproduction cross sections will be extracted and subjected to a longitudinal/transverse separation. This presentation will provide a brief overview of previous related experiments at Jefferson Lab, introduce the E12-13-010 experiment in Hall C, and present some preliminary results.

Speaker: Mr Yaopeng Zhang (Tsinghua University)

NPS Experiments in Hall C at Jefferson Lab.pdf

71 Unveiling Nucleon GPDs through Drell-Yan Processes

The contribution of parton orbital motion to the nucleon spin structure is encoded in transverse-momentum dependent distributions (TMDs) and generalized parton distributions (GPDs). These distributions are primarily accessed through lepton-induced processes such as semi-inclusive deep-inelastic scattering (SIDIS) and Deeply Virtual Compton Scattering (DVCS). As a complementary approach, measurements of (un)polarized Drell-Yan process with hadron beams provide a unique probe, allowing critical tests of the universality properties of TMDs and GPDs between space-like and time-like regimes.
In this talk, we will discuss the interesting results of TMDs results explored by the Drell-Yan process and present the future prospects for accessing nucleon GPDs via the measurements of exclusive pion-induced Drell-Yan process at J-PARC.

Speaker: Wen-Chen Chang (Institute of Physics, Academia Sinica)

SPIN2025_GPDatJPARC_wchang.pdf

72 Compton Form Factor Extraction using Quantum Deep Neural Networks

We present a comparative study of Compton Form Factor (CFF) extraction using pseudodata derived from Deeply Virtual Compton Scattering (DVCS) experiments at Jefferson Lab. The analysis is based on the twist-two formalism of Belitsky, Kirchner, and Müller, incorporating a minimally biased fitting strategy inspired by local fits to reduce model dependence. Two machine learning approaches are explored: Classical Deep Neural Networks (CDNNs) and Quantum Deep Neural Networks (QDNNs). Our results show that QDNNs generally outperform their classical counterparts in both accuracy and precision, particularly in scenarios constrained by limited model complexity with large experimental errors and data sparsity. These findings highlight the promising role of quantum-enhanced learning techniques in the extraction of hadronic structure observables and suggest a viable path forward for future quantum-optimized analyses in spin-dependent exclusive processes.

Speaker: Brandon Le (University of Virginia)

SPIN2025_CFF_QDNN.pdf

73 Recent Developments in perturbative calculations on DVCS

Deeply virtual Compton scattering (DVCS) is established as the golden channel for accessing generalized parton distributions (GPDs), which encode the nucleon's three-dimensional structure and are crucial for understanding the origin of nucleon spin. In this talk, I will summarize recent theoretical advances in predicting the DVCS process to higher perturbative orders. These developments are essential for analyzing upcoming high-precision measurements from the JLab 12 GeV upgrade, EIC, and EIcC, with the ultimate goal of precision nucleon GPD determination.

Speaker: Yao Ji

YJi_spin2025.pdf

74 Heavy vector meson production adoptingi GPD method

Exclusive heavy vector meson production is investigated in ep pp and pPb collisions employing GPD approach with GK model. Three sets gluon density are used to calculate exclusive heavy vetor meson production. The survival factors and equivalent photon approximation are applied to predict the exclusive heavy vector mesons photoproduction in proton-proton collisions. The GPD method prediction gives a good agreement with the experimental data at LHCb.

Speaker: Ya-Ping Xie (Institute of modern Physics of CAS)

Vector meson production using GPD method.pdf

15:40 Coffee break

75 Gravitational form factors from light front QCD

The energy-momentum tensor encodes the internal energy, spin, and stress distributions within hadrons, shedding new light on hadron structures and fundamental QCD problems such as confinement and the origin of hadron mass. In recent years, it has become possible to measure this quantity directly from experiments via generalized parton distributions, leading to growing interest in both experimental and theoretical studies. However, the dynamical nature of this observable poses a significant challenge, particularly for strongly coupled hadrons.

In this talk, I will discuss our recent progress in investigating the energy-momentum tensor and the associated gravitational form factors based on a nonperturbative light-front Hamiltonian approach. Our main result is a general, nonperturbative light-front wave function representation, which provides an adequate microscopic description. This representation is derived from a strongly coupled (3+1)-dimensional scalar field theory and is renormalized with a Fock sector-dependent scheme. It can be applied to various systems, including the charmonia, the pion, and the nucleon, with their respective light-front wave functions, offering new insights into the strong force within hadrons.

Speaker: Xianghui Cao (University of Science and Technology of China)

[XianghuiCao][2025-09-20] Spin2025.pdf

76 Gravitational form factors in the perturbative limit

The generalized distribution amplitudes (GDAs) have attracted attention in recent years because of their relation with the energy momentum tensor (EMT) form factors (FFs). The GDAs can be experimentally accessed through the study of amplitudes in $\gamma^{\ast} \gamma \to M_1 M_2$ and $\gamma^{\ast} \to M_1 M_2 \gamma$, where $M_1M_2$ is a pseudoscalar meson pair such as $\pi \eta $ and $\eta \eta^{\prime}$. In this paper we calculate these amplitudes in the perturbative limit where the $M_1M_2$ GDAs are expressed in terms of meson distribution amplitudes which have been constrained in the previous experiments. Our explicit calculation verifies the existence of a new EMT FF that breaks the conservation law of EMT when the hadronic matrix element of the EMT operator is examined for a single quark flavor. In addition, our result shows that the $M_1M_2$ GDAs are identical in $\gamma^{\ast} \gamma \to M_1 M_2$ and $\gamma^{\ast} \to M_1 M_2 \gamma$, which confirms the universality of GDAs in the perturbative limit. In future, the GDAs and EMT FFs studied in this paper can be investigated at Belle II. Our study enhances the accessibility to the $P$-wave GDAs in $\gamma^{\ast} \gamma \to M_1 M_2$ and $\gamma^{\ast} \to M_1 M_2 \gamma$ and gives a promising way to search for exotic hybrid mesons in the future experiment.

Speaker: Qin-Tao Song (Zhengzhou University)

spin2025-song.pdf

77 Gravitational and Electromagnetic Form Factors of Pion, Kaon, and Nucleon

This presentation offers a unified set of results for the elastic electromagnetic and gravitational form factors of the pion, kaon, and nucleon, using continuum Schwinger function methods. A key feature of the study is the consistent treatment of dressed graviton–quark interactions, allowing seamless analysis across mesons and baryons. We find that the mass radii of pions and kaons are smaller than their charge radii, in line with existing empirical insights, and that their internal pressures rival those inside neutron stars. Extending the approach to nucleons, we show that the pion’s near-core pressure is about twice that of the proton, with both exceeding neutron star values. A detailed decomposition of the nucleon’s gravitational form factors reveals a constant glue-to-quark ratio, independent of momentum transfer. We also establish a clear ordering of proton radii: mechanical < mass-energy < charge. These results provide timely guidance for future experiments probing the inner structure of hadrons and the dynamics of QCD.

Speaker: Minghui Ding (Nanjing University)

Minghui_Ding_spin2025.pdf

78 Baryon-antibaryon generalized distribution amplitudes

Baryon-antibaryon generalized distribution amplitudes (GDAs) give an access to timelike gravitational form factors (GFFs) which are complementary to the spacelike ones which can be deduced from the hadronic generalized parton distributions (GPDs) measured in deep exclusive electroproduction processes. They allow to probe the GFFs of unstable baryons in the baryon octet, since the second moments of hadronic generalized distribution amplitudes (GDAs) lead to the timelike GFFs.These GDAs can be measured in the process $e^+ e^- \to B \bar{B} \gamma$, in the generalized Bjorken regime where the invariant mass of the $B \bar{B}$ pair is near threshold at high energy facilities, such as BESIII, Belle II, and the proposed Super Tau-Charm Facility.In this work, we investigate this process using the QCD collinear factorization framework, where the scattering amplitudes are expressed in terms of the baryon timelike electromagnetic (EM) FFs and Compton FFs. We also provide a numerical estimate of the cross sections with a model for baryon-antibaryon GDAs.Our work provides us a possibility to extract the timelike baryon GFFs from near future experimental measurements,and these GFFs may be further used to study longstanding questions in hadronic physics such as the baryon spin decomposition and D-term.

Reference：Jing Han, B. Pire and Qin-Tao Song, arXiv:2506.09854 [hep-ph].

Speaker: Jing Han (Zhengzhou University)

Baryonantibaryon923-JingHan.pdf

Acceleration, storage and polarimetry of polarized beams: 01

Conveners: Frank Maas, Haixin Huang, Boxing Gou

Conveners: Boxing Gou (Institute of Modern Physics, CAS) , Zhe DUAN (高能所)

79 A Spin Tune Model for Spin Coherence Time Optimisation at Storage Rings

Electric Dipole Moments (EDMs) are very sensitive probes of physics beyond the Standard Model (SM). The JEDI collaboration aims to measure the EDMs of charged particles making use of polarized beams in a storage ring. Such a precision experiment requires the maximization of the Spin Coherence Time (SCT). To identify the working conditions that maximize the SCT, the spin tune of the single particles must be tracked with high precision.
With this experiment in mind, this paper presents a model that accurately tracks the spin tune in a variety of lattices representing existing storage rings as well as a future class of dedicated storage rings. These lattices differ in the combination of electric and magnetic fields used for particle confinement and the number of sextupole families. Furthermore, the parameters used in the model are shown to be directly accessible from beam diagnostics and sextupole field strengths via linear models. Finally, the study explores the implications of the model on the decoherence of a beam stored in such storage rings. The spin tune model outcomes were verified by comparison to those of the brute force searches of configurations with SCTs of more than 1000 seconds. The result was a deeper mathematical understanding of the phenomenon as well as a method to find the setting which optimizes the SCT.

Speaker: Rahul Shankar (University of Ferrara and INFN)

SPIN2025_Spin_Tune_Model.pptx

80 Spin Physics Research Infrastructure and Technologies at NICA (SPRINT@NICA).

The study of the spin effects and polarization phenomena in hadronic reactions is the traditional scientific direction of JINR. Nowadays Spin Physics Detector [1] at NICA as well as new spin projects at the fixed targets [2,3] at Nuclotron are in preparation. This research program requires the development of high intensity polarized beams, polarized targets, beam and focal polarimetry, systems of the spin manipulation and control.
The main goal of the SPRINT@NICA project is to provide the research infrastructure and to develop the technologies for the current and planned spin studies at Nuclotron/NICA. The spin transparency regime for polarized protons and deuterons over whole energy range of Nuclotron and NICA is discussed [4,5]. Further development of the Source of Polarized Ions [6] with corresponding deuteron and proton beam polarimeters is planned. The extension of the spin program to the search of axion-like particles [7] and measurement of the EDM with beams of polarized protons and deuterons [8] is discussed.

[1] V. Abazov et al. (SPD Collaboration) , Natural Science Review 1, 1 (2024).
[2] M. Janek et al., Few Body Syst. 63, 3 (2022),
V.P. Ladygin et al., Phys.Part.Nucl. 53, 251 (2022).
[3] S.N. Basilev et al., Eur.Phys.J.A 56, 26 (2020).
[4] Yu.N.Filatov, Phys.Part.Nucl. 56, 363 (2025).
[5] Yu.N.Filatov et al., JETP Lett. 116 , 413 (2022), JETP Lett. 118, 387 (2023),
JETP Lett. 120, 779 (2024).
[6] A.S. Belov et al., J.Phys.Conf.Ser. 938, 012017 (2017).
[7] S.Karanth et al., (JEDI Collaboration), Phys.Rev.X 13 , 031004 (2023).
[8] Yu.Senichev et al., Phys.Atom.Nucl. 87, 436 (2024).

Speaker: Vladimir Ladygin (Joint Institute for Nuclear Research, Dubna, Russian Federation)

VLadygin_SPRINT_SPIN2025v1.pdf

81 Polarimetry of pulsed H$^-$/D$^-$ ion beams: Extended applicability of the Lamb-shift polarimeter

Until 2023, a polarized H$^-$/D$^-$ ion source delivered pulsed negative ion beams for stripping injection into the COSY accelerator. Accurate and efficient measurement of the nuclear spin polarization directly behind the source is essential for precision experiments at COSY. A data acquisition system was developed to enable reliable, automated measurements with improved efficiency and to reduce operator intervention. To achieve that, the applicability of the Lamb-shift polarimeter has been successfully expanded to include pulsed H$^-$ and D$^-$ ion beams. The presented setup is useful and suitable to determine and optimize the polarization of upcoming polarized sources of the COSY type without pre-acceleration. We also present additional measurements of the nuclear spin polarization of H$_3^+$ ion beams with a Lamb-shift polarimeter.

Speaker: Simon Jakob Pütz (University of Cologne/GSI)

Spin2025SimonPuetz.pptx

82 BNL alternating gradient synchrotron with four helical magnets to minimize the losses of the polarized proton beam

The principle of using multiple partial helical magnets to preserve the polarization of the proton beam during its acceleration was applied successfully to the alternating gradient synchrotron (AGS) which currently operates with two partial helical magnets. In this paper we further explore this idea by using four partial helical magnets placed symmetrically in the AGS ring. This provides many advantages over the present setup of the AGS, which uses two partial helical magnets. First, the symmetric placement of the four helical magnets and their relatively lower field of operation allows for better control of the AGS optics with reduced values of the beta functions, especially near beam injection and allows both the vertical and horizontal tunes to be placed within the ‘‘spin tune gap,’’ therefore eliminating the horizontal and vertical intrinsic spin resonances of the AGS during the acceleration cycle. Second, it provides a wider spin tune gap. Third, the vertical spin direction during beam injection and extraction is closer to vertical. Although the spin tune gap, which is created with four partial helices, can also be created with a single or two partial helices, the high field strength of a single helical magnet which is required to generate such a spin tune gap makes the use of the single helical magnet impractical, and that of the two helical magnets rather difficult. In this paper we will provide results on the spin tune and on the optics of the AGS with four partial helical magnets, and compare them with those from the present setup of the AGS that uses two partial helical magnets. Although in this paper we specifically discuss the effect of the four partial helices on the AGS, this method which can eliminate simultaneously the vertical and horizontal intrinsic spin resonances is a general method and can be applied to any medium energy synchrotron which operates in similar energy range like the AGS and provides the required space to accommodate the four helices. In addition, the four partial helix solution is an optimum solution because it eliminates all the spin resonances for any synchrotron which operates in the same energy range as the AGS.

Speaker: Dr Nick Tsoupas (Brookhaven National Lab)

15:40 coffee break

83 Development and Testing of a 5 MeV Mott Polarimeter for Precision Measurement of Polarization for P2

The P2 experiment at Mainz Energy-Recovering Superconducting Accelerator (MESA) aims to measure the Weinberg angle with an uncertainty of 0.15%. This implies that the uncertainty of the beam polarization measurement must be less than 1%. To achieve this, a polarimetry chain with polarimeters operating at different energies and principles is being developed.

As a part of this polarimetry chain, a 5 MeV Mott polarimeter has been fabricated, installed, and tested at the MAMI facility. The results of these tests will be presented during this talk.

Speaker: Rakshya Thapa (Johannes Gutenberg University of Mainz)

Spin_2025.pdf

vi_00001_20250618_103935.mp4

84 Polarized beam studies for CEPC and BEPCII

This presentation will overview the study of polarized lepton beams in the context of resonant depolarization and longitudinal polarized colliding beams, for the 100km scale Circular Electron Positron Collider (CEPC), including design studies and R&D progress, as well as the potential of attaining longitudinal polarization at BEPCII.

Speaker: Prof. Zhe Duan (IHEP)

Polarization_studies_CEPC_BEPC.pptx

85 Hadron free measurement of electron beam polarization

Over the past few decades, polarized electron beams have been actively used in various fields of physics. Mott, Moller, and Compton scattering methods are used to diagnose the polarization of such beams. We propose to use a different method. The high charge densities achieved in electron beams offer the possibility of measuring the polarization by scattering one electron beam off another. Options for self-calibrating the beam are proposed, as well as an option for online polarization measurements.

Speaker: Valery Tyukin

SPIN-2025-09-23-VT.pdf

86 Design and implementation of a laser Compton polarimeter at BEPCII-U

As a key R&D item of polarized lepton beams for future colliders, a laser Compton polarimeter has been designed for the electron storage ring of BEPCII, reusing the X-ray beamline and experimental hutch of a dismantled wiggler source. This article will describe the design considerations of the Compton polarimeter, report the first phase beamline modification and preliminary beam commissioning results, and discuss potential performance improvements in the near future.

Speaker: Mengyu Su

SPIN2025_v4.pdf

SPIN2025_v4.pptx

Polarized ion and lepton sources and targets: 01

Conveners: Norihiro Doshita, Xiaqing Li

Conveners: Norihiro DOSHITA (Yamagata University) , Xiaqing Li (Shandong University)

87 Development of a Polarized H^+/D^+ Ion Source at IMP

Spin is a fundamental property of particles and plays a crucial role in particle structure and interactions. In a polarized ion beam, the spins of ions favor a particular direction, which is not only crucial for spin physics research but also beneficial for cutting-edge physics experiments that require high precision. For producing intense polarized ion beams, a Spin Polarized Ion Source (SPIS) is under development at the Institute of Modern Physics (IMP, CAS). It is intended to produce polarized proton (deuteron) ion beams of 1 mA, 25 keV, with 100 $\mu$s pulse width, 5 Hz repetition frequency and polarization of no less than 80%. In this paper, a SPIS consisting of a Polarized Atomic Beam Source (PABS) and a plasma ionizer will be presented. An advanced Lamb-shift Polarimeter (LSP) with a measurement precision of 1% that could be completed within a few seconds have been successfully tested. This polarized ion source will eventually be installed to the HIAF (High Intensity heavy ion Accelerator Facility) injector that will enable HIAF to deliver 9.3 GeV polarized proton and 4.6 GeV polarized deuteron beams. It will not only support a wide range of frontier physical experiments but also pave the way towards the Electron-Ion Collider in China (EicC) strategy.

Speaker: Mr Yaojie Zhai (Institute of Modern Physics, Chinese Academy of Sciences)

r2_Development of polarized ion source at IMP_SPIS2025.pdf

88 Development of a Polarized H/D atom Source for the EicC Project

The Electron-Ion Collider in China (EicC) is a proposed high-intensity facility designed to explore the partonic structure of nucleons and nuclei, particularly in the sea quark region, with unprecedented precision. Its physics program aims to uncover the origin of nucleon mass and spin, image the three-dimensional landscape of partons, study quark-gluon dynamics in nuclei, and search for exotic hadronic states. These ambitious objectives demand high-luminosity collisions involving polarized beams with both high intensity and polarization, making advanced polarized source development a crucial step.
A polarized hydrogen and deuterium (H/D) ion source is currently under development at the Institute of Modern Physics, following the Atomic Beam Polarized Ion Source (ABPIS) scheme. The target performance is a beam polarization above 0.8 and an ion beam intensity exceeding 1 mA. The system incorporates two sets of sextupole magnets and three radiofrequency transition (RFT) units, which have been carefully designed and optimized for high polarization efficiency.
So far, an H atomic beam flux exceeding 3×10¹⁶ atoms/s has been measured by a hot cathode ion gauge. When the weak field transition (WFT) unit placed between two sets of sextupole magnets is turned on, the atomic beam flux decreases by about 50% compared to when the WFT is turned off, indicating the occurrence of effective spin state transitions. Further RFT tests and beamline optimization are ongoing.

Speaker: SHENG ZHANG (The Institute of Modern Physics (IMP) of the Chinese Academy of Sciences)

Development of a Polarized H&D atom Source for the EicC Project - V5.pdf

Development of a Polarized H&D atom Source for the EicC Project - V5.pptx

89 Upgrading Polarized Beam Equipment at the JINR Accelerator Facility: Future Prospects

At the JINR accelerator complex, within the polarization research program of the NICA project, the high-intensity SPI source of polarized deuterons and protons and low-energy polarimeters are being developed for the SPI setup at the outlet and behind the 5 MeV/nucleon linear accelerator.
The status, upgrades of the above facilities, future prospects are presented.

[1] G.V. Trubnikov, N.N. Agapov, O.I. Brovko, A.V. Butenko, E.D. Donets, A.V. Eliseev, V.V. Fimushkin et al., Proc. of the 4th Int. Particle Accelerator Conf. IPAC2013, TUPFI009 1343 (2013).
[2] A.S. Belov, D.E. Donets, V.V. Fimushkin, A.D. Kovalenko, L.V. Kutuzova, Yu.V. Prokofichev, V.B. Shutov, A.V. Turbabin, and V.N. Zubets, J. Phys. Conf. Ser. 938, 012017 (2017).
[3] V.V. Fimushkin, A.D. Kovalenko, R.A. Kuzyakin, M.V. Kulikov, L.V. Kutuzova, Yu.A. Plis, Yu.V. Prokofichev, V.B. Shutov, A.S. Belov, A.V. Turbabin, and V.N. Zubets, PoS 324, 019 (2018).
[4] V.V. Fimushkin, R.A. Kuzyakin, M.V. Kulikov, L.V. Kutuzova, Yu.V. Prokofichev, A.M. Shumkov, A.S. Belov, A.V. Turbabin, and V.N. Zubets, PoS 346, 114 (2019).

Speaker: Viktor Fimushkin (Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow region, Russia)

03_SPIN2025_China_Fimushkin.pdf

90 Status of the polarized gas target for the LHCspin project

LHC at CERN is the world's highest energy collider, but it cannot accelerate polarized protons like BNL's RHIC. The LHCspin project will install a polarized hydrogen gas target in one of the accelerator rings of the LHC and use a 7 TeV proton beam and the polarized target to advance research into nucleon spin structure. In the first step, the polarized gas target and a simple particle detector will be installed at a location different from the collision point of existing experiments at the LHC, and basic polarization experiments will be performed. In the second step, the polarized gas target will be incorporated into the LHCb detector and precise polarization experiments will be performed.

The development of the polarized gas target is important for the project. Here I will show the status of the polarized target.

Speaker: Norihiro DOSHITA (Yamagata University)

LHCspin-target-doshita.pdf

91 Polarized solid target for possible future AMBER program at CERN

Recently COMPASS showed an interesting result on the d-quark Sivers TMD PDF via SIDIS process with muon beam and the polarized deuteron polarized target. It showed that the d-quark Sivers asymmetry had almost twice larger than u-quark at high-x region.

In order to understand the d-quark OAM contribution on the nucleon spin structure, further measurements via other processes like a Drell-Yan are required. The COMPASS collaboration measured the azimuthal asymmetries which relates to the Sivers TMD PDF via DY process with a negative pion beam and with a proton solid target in 2015 and 2018. We plan to use a positive pion beam and a polarized proton target to obtain a larger asymmetry on the Sivers TMD PDF.

Here I will discuss on the future possible polarized target for this program.

Speaker: Norihiro DOSHITA (Yamagata University)

Doshita-AMBER-PT.pdf

15:40 Break

92 Development of a Polarized H/D Gas Target at IMP

In high-energy nuclear physics, spin plays a crucial role in the composition of matter and the interaction between particles. The Institute of Modern Physics, Chinese Academy of Sciences, plans to develop polarized beams and targets for spin-related studies at the High Intensity heavy-ion Accelerator Facility (HIAF). The target is mainly composed of an atomic beam source, a target chamber and a Breit-Rabi polarimeter. Currently, design work for a high-performance polarized H/D gas target, including mechanical design and track/spin simulation, is ongoing.
In order to achieve high beam intensity and high degree of polarization, the spin-filtering sextupole magnets and the spin-flipping transition units, are emulated in terms of atomic spin\trajectory tracking and numerical calculations of hyperfine transition via solving the time-dependent Schrödinger equation. In this talk, I will present the current status of our target design, with an emphasis on key component optimization.

Speaker: Xiaorong Lv (Institute of Modern Physics, CAS)

spin2025-talk-lvxiaorong.pdf

Spin in heavy ion collisions: 02

Conveners: Enrico Speranza, Jinhui Chen, Takafumi Niida

Conveners: Xu-Guang Huang (Fudan University) , Zhenyu Chen (Shandong University)

93 Measuring spin alignment of D*+ mesons in pp and Pb–Pb collisions with ALICE

Heavy quarks, i.e. charm and beauty, are produced in the initial stage of the heavy-ion collisions, and can inherit a polarisation that is preserved through hadronisation and manifested in the spin state of the final hadron. This polarisation can be quantified via the spin density matrix element ρ₀₀, where deviations from 1/3 signal spin alignment. Measuring the spin alignment of vector mesons provides a unique means to investigate the transfer of quark polarisation through hadronisation and to explore the impact of the large initial angular momentum and magnetic field generated in non-central heavy-ion collisions.
In this contribution, we present the final measurements of the ρ₀₀ parameter for D⁺ mesons in pp and Pb–Pb collisions, obtained from the data samples collected by the ALICE experiment during LHC Run 2, together with preliminary results from the larger samples collected in Run 3, which allow to extend the transverse-momentum reach. The analysis is performed separately for promptly produced D⁺ mesons and for those originating from B-meson decays, the latter expected to be longitudinally polarized with respect to the helicity axis, owing to helicity conservation in weak decays.

Speaker: Mingze Li (CCNU)

SPIN_2025_mingze.pdf

94 Hyperon local polarization in pPb collisions at CMS

The observation of hyperon polarization along beam direction ($P_z$) in nucleus-nucleus collisions has opened a new way to study the complex vortical structures of the QGP. With the high-statistics data collected by the CMS experiment, we present the first $P_z$ results for $\Lambda$ and $\bar{\Lambda}$ particles in pPb collision at $\sqrt{s_{NN}}= 8.16$ TeV over a wide transverse momentum ($p_{T}$) and charged particle multiplicity ($N_\mathrm{trk}^\mathrm{offline}$) range. The $P_z$ values decrease as a function of $N_\mathrm{trk}^\mathrm{offline}$, but increase with $p_{T}$. A hydrodynamic model that describes the observed $P_z$ values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the pPb results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies.

Speaker: Chenyan Li

Chenyan_spin2025.pdf

95 Hydrodynamic effects on spin polarization in AA and pA collisions

We have implemented the 3+1 dimensional CLVisc hydrodynamics model with \trento-3D initial conditions to investigate the spin polarization of $\Lambda$ hyperons along the beam direction in p+Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV. Following our previous theoretical framework based on quantum kinetic theory, we consider three different scenarios: $\Lambda$ equilibrium, $s$ quark equilibrium, and iso-thermal equilibrium scenarios. We have computed the second Fourier sine coefficients of spin polarization along the beam direction, denoted as $\left\langle P_{z} \sin 2(\phi_{p} - \Psi_{2}) \right\rangle$, with $\phi_{p} - \Psi_{2}$ being the azimuthal angle relative to the second-order event plane $\Psi_{2}$, as functions of multiplicity, transverse momentum and pseudo-rapidity in the three scenarios. Additionally, we have also computed the spin polarization along the beam direction, $P_{z}$, as a function of the azimuthal angle. We find that the spin polarization induced by thermal vorticity always provides an opposite contribution compared to the shear-induced polarization in p+Pb collisions. The total spin polarization computed by the current hydrodynamic model disagrees with the data measured by LHC-CMS experiments.

Speaker: Cong Yi (USTC)

Spin2025_Cong-Yi.pdf

96 Is the shear induced spin polarization non-dissipative?

The shear-induced polarization plays a crucial role in understanding the local polarization of Λ and Λ⎯ hyperons. A key puzzle is whether the shear-induced polarization is non-dissipative or not. In this work, we analyzed the shear-induced polarization and the anomalous Hall effects using the entropy flow and H-theorem introduced from quantum (chiral) kinetic theory. While the shear-induced polarization and the anomalous Hall effect do not directly contribute to the entropy production rate, the perturbations associated with the shear tensor lead to an increase in entropy, similar to the role of the shear tensor in classical kinetic theory. We also examined these effects within the framework of linear response theory using Zubarev's approach. These findings highlight the limitations of the current theoretical framework in fully characterizing the dissipative properties of these phenomena.

Speaker: Jia-rong Wang (中国科学技术大学)

entropy_SPIN2025_20250923_2.pdf

15:30 Coffee break

97 Color-field induced spin transport in high-energy nuclear collisions

Despite the successful description of global polarization of $\Lambda$ hyperons in heavy ion collisions through thermal voricity, the follow-up observations of local spin polarization and spin alignment of vector mesons further indicate the presence of additional mechanisms upon spin transport of quarks in the QCD medium. In high-energy nuclear collisions, the soft thermal gluons in the quark gluon plasma phase or the overpopulated gluons in the glasma phase as its precursor in the color-glass-condensate effective theory may be delineated by fluctuating chromo-electromagnetic fields (or color fields for short). By employing the recently developed quantum kinetic theory of quarks with phenomenological models and approximations, we study the momentum dependence for dynamical spin alignment of $\phi$ mesons from longitudinally dominant color fields in the glasma phase. Also, the non-dynamical spin alignment coming from soft thermal gluons characterized by isotropic color fields in the quark gluon plasma is qualitatively analyzed for comparison. Moreover, we investigate how color-field correlators along with anisotropic quark flow could generate local spin polarization from the corona of the glasma, which may play a significant role on longitudinal polarization of $\Lambda$ hyperons particularly in small collision systems.

Speaker: Di-Lun Yang (Academia Sinica)

SPIN2025_DLYang.pdf

98 An improved formula for spin polarization at local thermodynamic equilibrium

We present an upgraded formula for Wigner function and spin polarization of fermions emitted by a relativistic fluid at local thermodynamic equilibrium at the freeze-out which improves the one obtained in literatures and used in numerical simulations of relativistic nuclear collisions. By using a
new expansion method applicable to freeze-out hypersurfaces with arbitrary geometry, we reproduce the known term proportional to thermal vorticity and obtain a better approximation for the spin-shear term. The new method captures the long-distance interference along the particle’s trajectory, which was missed in previous approaches. It also naturally excludes contributions from space-time gradients in the normal direction of the hypersurface, providing a theoretical justification for the isothermal condition previously imposed a priori. This framework can be extended to particles with arbitrary spin.

Speaker: Dr Xin-Li Sheng (Firenze University and INFN Firenze)

Spin-2025-Sheng-XinLi.pdf

99 Measurement of the J/$\psi$ polarization in pp and Pb--Pb collisions with ALICE at the LHC

Quarkonia production in high-energy proton-proton (pp) collisions serves as an important probe for studying quantum chromodynamics (QCD) in vacuum. Understanding the production mechanism of the J/$\psi$, a bound state of a charm and anticharm quark, is essential for constraining both perturbative and non-perturbative aspects of QCD calculations. The polarization of quarkonia in pp collisions is a powerful observable for distinguishing between various QCD-based models of quarkonium production. Furthermore, J/$\psi$ polarization measurements in pp collisions provide a valuable reference for investigating the behavior of charmonium in the quark-gluon plasma formed in nucleus-nucleus collisions.

In this contribution, we will present the first preliminary results of the inclusive J/$\psi$ polarization measurement via the dielectron decay channel at midrapidity (|y| < 0.9) in pp collisions at $\sqrt{s} = 13.6$ TeV. This analysis will be discussed alongside previous J/$\psi$ measurements at forward rapidity and related results, including vector mesons such as $\phi$ and $K^*$ in pp collisions from ALICE Run 2 data. Additionally, the J/$\psi$ polarization with respect to the event plane in heavy-ion collisions will also be discussed.

Speaker: Xiaozhi Bai (University of Science and Technology of China)

XiaoZhiBai_spin_xbai_v2.pdf

100 Measurements of hyperon spin correlation in Au+Au collisions at BES-II energies at STAR

The observation of hyperon global polarization and vector meson spin alignment in heavy-ion collisions has revealed that spin phenomena are important probes of quark matter properties. These findings point toward possible spin correlations between quarks and antiquarks in the quark-gluon plasma. Such correlations are sensitive to production mechanism and evolution dynamics of spin polarization, as well as the interplay between spin and the other dynamical degrees of freedom in the collision system. In this talk, we report the status of spin correlation measurements of Lambda-(anti)-Lambda hyperon pairs in Au+Au collisions at BES-II energies (7.7-27 GeV) at RHIC-STAR. The results provide insights into the spin polarization mechanism in heavy-ion collisions, and shed light on fundemental properties of strong interactions and color confinement.

Speaker: Xingrui Gou

SPIN2025_Xingrui_v8.pdf

101 Chiral phase transition and spin alignment of vector mesons with chiral imbalance in a rotating QCD medium

We study the two-flavor Nambu-Jona-Lasinio model under the rotation and chiral chemical potential μ5. First, the influence of chiral imbalance on the chiral phase transition in the Tpc − ω plane is investigated. Research manifests that, as μ5 increases, the critical point of the Tpc − ω plane chiral phase transition will move closer to the T axis. This means that the chiral chemical potential μ5 can significantly affect the Tpc − ω phase diagram and phase transition behavior. While discussing the Tpc − ω phase diagram, we also study the spin alignment of the ρ vector meson under rotation. In the study of the spin alignment of the
vector meson ρ, ρ00 is the 00 element of the spin density matrix of vector mesons. At high temperatures, ρ00 is close to 1/3, which indicates that the spin alignment of the vector meson ρ is isotropic. The study found that, under finite rotation, increasing the chiral chemical potential μ5 can significantly enhance ρ00 around the phase transition temperature. When rotational angular velocity is zero, ρ00 is close to 1/3, but as ω increases, ρ00 significantly decreases and deviates 1=3, indicating that rotation can significantly cause polarization characteristics. The ρ00 − r relationship near the phase transition temperature is studied. It is found that the farther away from the center of rotation, the lower the degree of spin polarization of the system. It is also found that the influence of chiral imbalance on the ρ00 − r relationship is also significant.

Speaker: Sheng-Qin Feng (Three Gorges University)

5_2025 S.-Q. Feng（Spin Physics).pdf

102 Spin alignment of vector mesons induced by spin density fluctuation

In recent years, spin polarization of hyperons and the spin alignment of vector mesons were observed by STAR in 20%-60% centrality collision, where the large angular momentum and the magnetic field were supposed to be the main reasons. However, in the most central collision with collision energy 200GeV, the rotation, magnetic field as well as the baryon number should vanish, spin alignment was also observed. Thus, it still remains challenge to explain the experimental data.

In this talk, I will present a new mechanism for the spin alignment of vector mesons: the spin density fluctuation. It is found that the spin alignment of vector meson is sensitive to the spin of constituent strange but is independent of the sign of the spin density, i.e., whether there is more spin-ups than spin-downs or vice versa, the same spin alignment of vector will be obtained. And due to interactions between quarks, especially the tensor and axial-vector interaction, the local spin density will not stay exact zero due to the fluctuation. Thus, though there is no global spin polarization of quarks, local spin density fluctuation will result in none zero spin alignment of vector meson. It is also found that the quark interactions induced by (anti-)instanton could be the source of spin alignment of phi and K^{*0} mesons.

Speaker: Kun Xu (BIT)

XuKun-SpinAlignment-SPIN2025.pptx

Spin in nuclear reactions and nuclei: 01

Conveners: Elena Long, Raphaël Dupré, Wim Cosyn

Conveners: Dmitriy Toporkov (Budker Institute of Nuclear Physics) , Ronggang Ping (IHEP)

103 Tensor-polarized parton distribution functions for spin-1 hadrons

Structure functions of the spin-1 deuteron will be investigated experimentally from the late 2020's at various facilities such as Thomas Jefferson National Accelerator Facility, Fermi National Accelerator Laboratory, nuclotron-based ion collider facility (NICA), and electron-ion colliders. We expect that a new high-energy spin-physics field could be created by these projects. In this paper [1], the current theoretical status is explained for the structure functions of spin-1 hadrons, especially on parton distribution functions, transverse-momentum dependent parton distributions, and fragmentation functions.

Reference
[1] S. Kumano, Euro. Phys. J. A 60 (2024) 205.

Speaker: Shunzo Kumano (IMP / KEK)

Kumano-Spin-2025-spin-1-2025-09.pdf

104 Hidden-Color Effects in Deuteron Structure

We explore the internal structure of the deuteron within the light-front framework, going beyond the traditional proton–neutron description. By incorporating hidden-color degrees of freedom, we model the deuteron as an effective mixture of singlet–singlet and octet–octet color configurations. Our study includes both unpolarized and polarized observables, including the tensor-polarized structure function $b_1$, as well as electromagnetic form factors. The results highlight the important role of hidden-color components in shaping the deuteron’s spin and partonic structure, providing insights for future spin physics experiments.

Speaker: Satvir Kaur

SK-SPIN2025.pdf

105 Role of reaction mechanisms in deuteron-proton elastic scattering at GeV energies

The deuteron-proton elastic scattering process is considered in the relativistic
expansion framework. Four reaction mechanisms are taken into account: one-nucleon-exchange,
single-scattering, double-scattering terms, and delta-isobar excitation in the intermediate state.
Each of these terms contributes into the reaction amplitude.
The model calculates the reaction amplitude, which makes it possible to find the angular dependence
of both the differential cross section and any polarization observables. In this report, I present
deuteron and proton analyzing powers, as well as the proton-to-proton polarization transfers in comparison
with the data at the deuteron energy of 1.6 GeV.

Speaker: Nadezhda Ladygina (JINR LHEP)

Ladygina_Spin2025.pdf

106 Nuclear effects on longitudinal-transverse structure function ratio

It has been assumed that nuclear modification does not exist in the longitudinal-transverse structure function ratio $R_N=F_L^N/(2xF_1^N)$ in lepton deep inelastic scattering. This assumption is widely used in obtaining structure functions of the ``nucleon" from nuclear data such as the deuteron ones. However, nuclear modifications do exist theoretically at least at medium- and large-$x$ regions because nucleons in a nucleus move in any direction, which is not necessary the longitudinal direction of the virtual-photon or weak-boson momentum in lepton scattering. Because of this transverse motion, the nucleon's transverse and longitudinal structure functions should mix with each other in nuclei with the mixture probability proportional to the nucleon's transverse momentum squared $\vec p_T^{\,\, 2}/Q^2$. In this work [1], numerical results are explicitly shown on such nuclear modifications in the deuteron. These nuclear modifications are important for determining precise structure functions of the nucleon. Furthermore, modifications of $R_N$ should be investigated also at small $x$ by the future electron-ion collider to find interesting gluon dynamics in nuclei. Hopefully, this nuclear effect on $R_N$ could be found by future experimental measurements at lepton accelerator facilities.

Reference
[1] S. Kumano, arXiv:2506.18305.

Speaker: Shunzo Kumano (IMP / KEK)

Kumano-Spin-2025-R-mod-2025-09.pdf

15:40 break

107 Status of experiments with polarized deuteron target at VEPP-3 electron storage ring

The report describes the production of an internal polarized deuteron target for experiments at the VEPP-3 electron storage ring. A description of the measurement of the average target polarization during the experiments is given. The schemes of the system for tagging photons that caused reactions, as well as the system for registering reaction products are presented. The results of the experiments on measuring the component of tensor analyzing power T20 in reactions of negative pi-meson photoproduction γd → ppπ−, and deuteron photodisintegration γd → pn are presented.

Speaker: Dmitriy Toporkov (Budker Institute of Nuclear Physics)

5_SPIN2025_Toporkov.pdf

108 Spin studies with polarized beams at the Nuclotron internal target

Nuclotron Accelerator Complex gives the opportunity to study spin effects using polarized deuteron and proton beams from Source of Polarized Ion. Recent results on the spin effects in deuteron-proton and proton-proton elastic scattering sensitive to the short-range spin structure of the nucleon-nucleon correlations obtained at the internal target at Nuclotron are discussed.
The further perspectives in spin physics program, in the development of the beam polarimetry and proton spin manipulation techniques at Nuclotron are disscussed.

Speaker: Vladimir Ladygin (Joint Institute for Nuclear Research, Dubna, Russian Federation)

VLadygin_DSS_SPIN2025.pdf

109 [Cancelled] Application of Deep Learning in Polarized Target Nuclear Magnetic Resonance Measurements

Continuous wave Nuclear Magnetic Resonance (NMR) with constant current has been pivotal in solid-state polarized target experiments within Nuclear and High Energy Particle physics. Phase-sensitive detection using a Liverpool Q-meter is conventionally employed for monitoring polarization during scattering experiments. Yet, when operating outside of designed operational parameters, there are significant nonlinearities have not yet been well understood for high-fidelity running. Additionally under experimental conditions low signal to noise can lead to much larger experimental uncertainties reducing the overall figure of merit of the scattering experiments. This presentation discusses recent advancements aimed at enhancing data acquisitions in NMR-based polarization measurements and extending the operational capabilities of the Q-meter beyond its designated parameters using machine learning (ML) to analyze measurements with a low signal-to-noise ratio (SNR), corresponding to high noise levels. This innovative approach enables more effective real-time online polarization monitoring and offline data analysis, thereby enhancing the overall performance metrics in scattering experiments involving Spin-1 target material.

Speaker: Devin Seay (University of Virginia)

110 Revealing Proton Spin Polarization via Hypertriton Production in Nuclear Collisions

Ultra-relativistic nuclear collisions create the quark–gluon plasma (QGP) known as the hottest, least viscous, and most vortical fluid ever produced in terrestrial laboratories. Its vortical structure has been uncovered through the spin polarization of Lambda ($\Lambda$) hyperons, attributed to the spin–orbit coupling that transfers the system’s orbital angular momentum to the quark spin, which is then inherited by hadrons via quark recombination or coalescence. However, $\Lambda$ polarization reflects primarily the strange-quark component, leaving the spin dynamics of the up and down quarks largely unexplored. Although the proton is an ideal probe, its stability makes direct measurements experimentally challenging.
Here, we propose to unravel proton spin polarization via hypertriton measurements, exploiting the fact that spin information is preserved when polarized nucleons and $\Lambda$ coalesce to form hypertriton. We show that, over a broad range of collision energies, the polarizations of proton, $\Lambda$, and hypertriton are related by a simple linear scaling law. Since both $\Lambda$ and hypertriton polarizations can be measured via their self-analyzing weak decays, this linear relation provides a practical experimental avenue for accessing spin polarizations of protons and neutrons–the dominant baryonic degrees of freedom in nuclear collisions.

Speaker: Daineng Liu (Fudan University)

Spin2025_Qingdao_dnliu.pdf

ISPC meeting

Wednesday, 24 September

3-dimensional structure of nucleon - TMD: 1

Conveners: Christopher Dilks, Andrea Signori, Ting Lin

Conveners: Yiyu Zhou (Department of Physics, University of Turin, via Pietro Giuria 1, I-10125 Torino, Italy) , Zhihong Ye (Tsinghua University)

111 CLAS12 experiments with a transversely polarized target

In the recent years, it has been realized that deep-inelastic scattering with polarization control could provide a variety of spin and azimuthal angle dependent observables sensitive to the quark-gluon interactions. New parton distributions and fragmentation functions have been introduced to describe the rich complexity of the hadron structure and move towards a multi-dimensional imaging of the underlying parton correlations. Besides the hard probe scale, these functions explicitly depend on the parton transverse degrees of freedom at the scale of confinement. Their study promises to open a unprecedented gateway to the peculiar nature of the strongly interacting force.

The CLAS12 experiments with a transversely polarized target (Run-Group H, or RGH) will have a unprecedented sensitivity to several crucial observables whose current knowledge is severely limited by the sparse data available. Distinctive features, common to all three RGH experiments, are the precise measurement of parton distributions and phenomena in the poorly explored valence region (large Bjorken-x) where current models project their magnitude to be peaking, a luminosity at least one order of magnitude higher than the previous experiments, a large acceptance detector for the disentanglement of the various correlations and kinematic regimes, and an excellent particle identification capability to access flavor sensitivity.

This work presents a selection of upcoming measurements planned at CLAS12 to address the mysteries of the nucleon structure from a modern point of view.

Speaker: Marco Contalbrigo (INFN Ferrara)

SPIN_250924_Marco.pdf

112 Central rapidity Jet transverse single spin asymmetry measurements in proton-proton collisions with sPHENIX

Jet transverse single spin asymmetries, $A_N$, are only sensitive to the
initial state effects as final state effects are not present. They are
therefore an excellent tool to single out the quark-gluon and tri-gluon
correlation functions that are the higher-twist equivalents to the
transverse momentum moments of the Sivers functions for quarks and
gluons. sPHENIX has taken transversely polarized proton-proton collision
data at $\sqrt{s} = 200 \, GeV$ using a large acceptance full electromagnetic
and hadronic calorimetry to reconstruct jets. The status of the jet $A_N$
measurements will be presented.

Speaker: Genki Nukazuka

Nukazuka_inclusive_jet_A_N_SPIN.pdf

113 Transverse Single Spin Asymmetry of Electromagnetic Jets at Forward Rapidity in p↑+p Collisions at STAR

Transverse single spin asymmetries (TSSAs, denoted AN ) in transversely
polarized p↑ + p collisions provide critical insights into the proton’s spin structure, yet their unexpectedly large magnitudes at forward rapidities remain a
puzzle. Observed across experiments, including those at RHIC, these asymmetries have yet to be fully explained by theoretical models, such as those based on
twist-3 contributions in collinear factorization or transverse momentum depen-
dent (TMD) parton distributions. Recent STAR measurements suggested that
diffractive processes may contribute significantly to the observed AN , prompting
a deeper investigation into their role.
This talk presents precise measurements of AN for electromagnetic jets in in-
clusive and diffractive processes from p↑ +p collisions at √s = 200 and 510 GeV,
collected using the Forward Meson Spectrometer at STAR (2.5 < η < 4.2). By
isolating diffractive contributions, these results quantify their impact on inclu-
sive AN , providing new constraints on the underlying mechanisms, advancing
our understanding of the origins of large TSSAs at forward rapidities.

Speaker: Weibin Zhang (UC Riverside)

SPIN2025.pdf

114 Measurement of the transverse single spin asymmetry for forward neutral pions in (non-)diffractive like events at RHICf and STAR

The transverse single-spin asymmetry ($A_{\mathrm{N}}$) serves as a crucial probe for understanding the mechanisms of particle production in polarized high energy particle collisions as well as the internal dynamics of quarks and gluons within a polarized nucleon. The RHICf collaboration measured a non-zero transverse single-spin asymmetry ($A_{\mathrm{N}}$) for very forward ($\eta > 6$) neutral pions ($\pi^{0}$) in transversely polarized $p+p$ collisions at $\sqrt{s} = 510$ GeV within the STAR experiment. This measurement, along with a similar analysis performed at STAR for forward $\pi^{0}$s, $2.7 < \eta < 4.0$, suggests that diffractive interactions could be primarily responsible for the observed $A_{\mathrm{N}}$. To quantitatively determine the extent to which diffractive and non-diffractive processes contribute to the RHICf $A_{\mathrm{N}}$, we conduct a joint analysis of the very forward $\pi^{0}$ $A_{\mathrm{N}}$ using both RHICf and STAR detector systems from the same collisions. We report preliminary results of $\pi^{0}$ $A_{\mathrm{N}}$ in diffractive-like and non-diffractive-like event categories, and discuss the current status of this ongoing analysis.

Speaker: Seunghwan Lee (RIKEN, Sejong University)

SPIN2025_Seunghwan.pdf

10:00 Coffee Break

115 Neutral meson transverse single spin asymmetries and prospects for the D0 transverse single spin asymmetry in polarized proton collisions with sPHENIX

Neutral mesons transverse single spin asymmetries, $A_N$, provide insights
into the spin-orbit correlations inside the nucleon via higher twist
correlation functions. As forward rapidities they are known to be very
large while at central rapidities vanishing asymmetries have been
measured. The sPHENIX experiment with electromagnetic calorimetry over a
rapidity range from -1.1 to 1.1 will allow to extend the central
rapidity measurements performed by PHENIX and therefore access a region
that has not been covered well, yet.
The latest results from the 2024 proton-proton collisions at $\sqrt{s}=200\,$GeV will be presented.

Speaker: Devon Loomis

SPIN2025_sPHENIX_Loomis.pdf

116 Energy Independence of the Collins Asymmetry in pp Collisions

The study of the Collins asymmetry in $p^{\uparrow}p$ collisions provides a crucial experimental probe for quark transversities and polarized transverse-momentum-dependent (TMD) fragmentation functions.
In this talk, we present high-precision measurements of the Collins asymmetry for $\pi^{\pm}$ within jets from transversely polarized ${p^{\uparrow}p}$ collisions at $\sqrt{s}$ = 510 GeV by using the STAR detector.
In terms of an energy-scaled jet transverse momentum ratio, $x_{\mathrm{T}} = 2p_{\mathrm{T,jet}}/\sqrt s$, a remarkable consistency is observed for Collins asymmetry of $\pi^{\pm}$ between $\sqrt{s}$ = 200 GeV and 510 GeV. This indicates that the Collins asymmetry is nearly energy independent, with at most a mild scale dependence, in $p^{\uparrow}p$ collisions.
The experimental results are compared to theoretical calculations, including models with and without TMD evolution.
Thus, these results enable unique tests of evolution and universality in the TMD formalism, providing important constraints for the transversity distributions and the Collins fragmentation functions.

Speaker: Yixin Zhang (Shandong University)

SPIN2025_YixinZhang.pdf

117 First-Principle Calculation of Collins-Soper Kernel from Quasi-Transverse-Momentum-Dependent Wave Functions

We present a lattice QCD calculation of the Collins-Soper kernel, which governs the rapidity evolution of transverse-momentum-dependent (TMD) distributions, using Large Momentum Effective Theory (LaMET). Quasi-TMD wave functions are computed with three meson momenta on CLQCD configurations (multiple lattice spacings) employing clover quarks and varied hadronic states. HYP smearing is applied to staple-shaped gauge links and Wilson loops to enhance signal-to-noise ratios. Divergences are systematically addressed: linear divergences via Wilson-line renormalization and logarithmic divergences through a self-renormalization-inspired scheme.

By combining two-loop light-cone matching, renormalization group evolution, and leading renormalon resummation, we determine the Collins-Soper kernel for transverse separations up to 1 fm, with extrapolation to large-momentum and continuum limits. This work provides critical inputs for soft functions and precision studies of TMD physics, advancing first-principles QCD in high-energy phenomenology.

Speaker: Jin-Xin Tan (Shanghai Jiao Tong University)

CS_kernel_in_LQCD_9_24_SPIN25.pptx

118 Unifying the study of leading and sub-leading twist PDFs within Dyson-Schwinger equations approach

We study the pion's leading and sub-leading twist PDFs, i.e., f(x) and e(x), using a newly developed technique within Dyson-Schwinger equations approach. We will show how the complexities brought by high Fock-state components, zero mode issue and dynamical chiral symmetry breaking can be handled in a consistent and symmetry-preserving framework that connects continuum QCD dynamics to observable partonic structure.

Speaker: Chao Shi (Nanjing University of Aeronautics and Astronautics)

202509_青岛.pdf

3-dimensional structure of nucleon - TMD: 2

Conveners: Christopher Dilks, Andrea Signori, Ting Lin

Conveners: Shu-yi Wei (Shandong University) , Valentin Moos (NYCU)

119 Measurement of Anti-Quark Sivers Asymmetry at FNAL-SpinQuest

SpinQuest at Fermilab is a fixed-target experiment to primarily measure the Drell-Yan process using transversely polarized NH$_3$ and ND$_3$ targets and unpolarized 120-GeV proton beam. In the Drell-Yan process, a quark in one scattering hadron and an anti-quark in the other hadron annihilate into a virtual photon and then decay into a muon (lepton) pair. The angular distribution of final-state muon pairs with respect to the target polarization is sensitive to the Sivers function of light anti-quarks in the nucleon, which is one of the eight leading-twist Transverse Momentum Dependent (TMD) parton distribution functions. The Sivers function of each anti-up and anti-down quarks can be extracted by the use of the NH$_3$ and ND$_3$ targets for $p$+$p$ and $p$+$d$ reactions. The intensity of the proton beam is as high as $2\times10^{12}$ protons/second, in order to accumulate the required number of Drell-Yan events. The $J/\psi$ and $\psi'$ productions are measured together, which is also sensitive to the Sivers functions of light anti-quarks and gluons. SpinQuest commissioned the target and the spectrometer with the proton beam in May-July 2024. The status of analyses of the commissioning data and preparation for the next data taking will be presented.

Speaker: Stephen Pate (New Mexico State University)

SPIN2025_SpinQuest.pdf

120 Semi-inclusive deep inelastic scattering off a tensor-polarized spin-1 target

We investigate semi-inclusive deep inelastic scattering (SIDIS) off a tensor-polarized spin-1 target, focusing on the production of an unpolarized hadron. We derive a comprehensive differential cross-section expression, characterized by 23 structure functions, which depend on the target spin states and the azimuthal distribution of the final-state hadron.
Within the TMD factorization framework, we perform a tree-level calculation of the hadronic tensor using quark-quark correlator and quark-gluon-quark correlator up to twist-3.
This yields 21 nonvanishing structure functions at leading and subleading twist, expressed in terms of TMD PDFs and TMD FFs. The measurement of these nonzero structure functions can be utilized to explore the tensor-polarized structure for spin-1 particles, offering insights into their internal dynamics.

Speaker: Dr Jing Zhao (Shandong University )

SPIN2025_JingZhao.pdf

121 Exploring Sivers Effects in SIDIS Vector Meson Production

We investigate the Sivers asymmetry in the production of vector mesons, specifically $\rho^0$ and $K^*$, in SIDIS processes in the TMD factorization framework. By employing the Sivers function extracted from pion and kaon production data, we calculate the transverse single-spin asymmetry for $\rho^0$ production and compare it with recent COMPASS measurements. Our results align well with the experimental data, supporting the universality of the Sivers function across different final-state hadrons within current uncertainties. Additionally, we provide predictions for the Sivers asymmetries of $\rho^0$ and $K^*$ mesons at the kinematics of EIC and EicC. While two kind of parametrizations of the Sivers function describe COMPASS data equally well, they yield distinct predictions at EIC and EicC, indicating that future high-precision data will better constrain the Sivers function and nucleon spin structure.

Speaker: Zhou Yajin (Shandong University)

spin2025_YZ.pdf

122 Isolated Photon transverse single spin asymmetries with sPHENIX

Direct photon single spin asymmetries, $A_N$, have the advantage that they
are not sensitive to final state effects and that the hard scattering
process is predominantly quark-gluon scattering at RHIC energies.
Therefore, direct photons provide a clean probe to study the quark-gluon
and tri-gluon correlations in single spin asymmetries with particularly
the latter hardly constrained at present. The larger and more hermetic
acceptance of sPHENIX compared to PHENIX is expected to improve the
precision of the previous direct photon AN measurements using the 2024
polarized proton-proton collisions that were recorded in sPHENIX.
The status of the direct photon $A_N$ measurements will be presented.

Speaker: Jaein Hwang (Korea University)

SPIN2025_DirectPhoton_fin.pdf

10:00 Coffee Break

123 Suppression of Spin Transfer to $\Lambda$ in Deep Inelastic Scattering

We investigate $\Lambda$ production in semi-inclusive deep inelastic scattering using a polarized lepton beam and find that the spin transfer is significantly suppressed by target fragmentation. As further demonstrated by a model estimation, experimental data can be well described once the target fragmentation is taken into account. Our findings suggest that, at the medium-energy scales of existing fixed-target experiments, such as JLab, COMPASS and HERMES, the separation of current and target fragmentation regions is not distinct. The spin suppression effect from target fragmentation not only alleviates the tension between data and theoretical predictions with current fragmentation, but also provides a new perspective to explore the hadronization mechanism. This effect can be further tested at high energy levels in the future experiments.

Speaker: Xiaoyan Zhao (Shandong University)

Zhao_spin2025.pdf

124 Quenching of polarized jets

Jets produced in association with a ${Z^0}$ or ${W^\pm}$ boson in hadronic collisions are naturally polarized due to the parity violation of weak interaction, making these processes ideal for extracting information about the longitudinal spin transfer $G_{1L}$, and for studying the phenomenon of polarized jet quenching. In this work, we compute the polarization of $\Lambda$ hyperons in $pp$ collisions and investigate the nuclear modification due to the jet-medium interaction in $AA$ collisions. We demonstrate that this quantity is a sensitive probe to the energy loss effect.

Speaker: Mr Wenhao Yao (Shandong University)

Quenching of polarized jets_spin2025.pdf

125 Measurement of $\Lambda\bar{\Lambda}$ spin correlation in proton-proton collisions at STAR

According to current understanding, the QCD vacuum contains a condensate of quark-antiquark pairs: $u\bar{u}$, $d\bar{d}$, and $s\bar{s}$. Due to the vacuum’s quantum numbers, $J^{PC} = 0^{++}$, these pairs are expected to appear as maximally entangled spin-triplet states with aligned spins. A recent proposal suggests that the $s\bar{s}$ pairs in the quark condensate may be experimentally probed through measurements of spin-spin correlations in $\Lambda\bar{\Lambda}$ hyperon pairs. In this talk, we present the first experimental measurements of spin-spin correlations for $\Lambda\bar{\Lambda}$, $\Lambda\Lambda$, and $\bar{\Lambda}\bar{\Lambda}$ pairs in $p+p$ collisions at $\sqrt{s} = 200\,\textrm{GeV}$, recorded by the STAR detector in 2012. Both short-range ($|\Delta y| < 0.5$ and $|\Delta \phi| < \pi/3$) and long-range ($0.5 < |\Delta y| < 2.0$, or $\pi/3 < |\Delta \phi| < \pi$) $\Lambda$ hyperon pairs are analyzed. For the first time, a significant spin-spin correlation is observed in short-range $\Lambda\bar{\Lambda}$ pairs, consistent with their origin in the hadronization of maximally spin-entangled $s\bar{s}$ pairs from the QCD vacuum. These results also offer valuable insight into the strange quark hadronization, the spin structure of the $\Lambda$ hyperon, and mechanisms of the spin transfer from polarized protons to $\Lambda$ hyperons.

Speaker: Qinghua Xu (Shandong University)

SPIN_2025_Vanek_final.pdf

126 Measurement of transverse polarization of $\Lambda$/$\bar{\Lambda}$ inside jets in unpolarized $pp$ collisions at $\sqrt{s}=200$ GeV

The fragmentation process has been proposed as a possible origin of the transverse $\Lambda$ polarization, described by polarizing fragmentation functions (pFFs). In $pp$ collisions, this mechanism can be studied by measuring the $\Lambda$ polarization within jets. We present the first measurement of the transverse polarization of $\Lambda$/$\overline{\Lambda}$ hyperons relative to the jet axis in unpolarized $pp$ collisions at $\sqrt{s}=200$ GeV, using high-statistics data from the STAR experiment. The dependence of the $\Lambda$ polarization on the jet transverse momentum ($p_T^{\text{jet}}$) is observed. The polarization is also studied as a function of the jet momentum fraction ($z$) carried by the $\Lambda$/$\overline{\Lambda}$, and the $\Lambda$/$\overline{\Lambda}$ momentum transverse to the jet axis ($j_T$). These results provide a critical test of the pFFs universality and new insights into the mechanisms behind the transverse $\Lambda$ polarization.

Speaker: Taoya Gao (Shandong University)

Spin2025_gty_20250922_new_v10.pdf

127 Measurement of $\Lambda/\bar{\Lambda}$ Transverse Polarization within Jets in $pp$ Collisions at $\sqrt{s}=510$ GeV

The transverse polarization of $\Lambda$ hyperons in unpolarized hadron--hadron reactions, first observed decades ago, is still not fully understood. The polarizing fragmentation functions, which are expected to contribute to the $\Lambda$ polarization, can be investigated by measuring the $\Lambda/\bar{\Lambda}$ transverse polarization inside jets in $pp$ collisions. In this contribution, we will present the status of our analysis on $\Lambda/\bar{\Lambda}$ polarization within jets based on $pp$ collisions at $\sqrt{s}=510\,\text{GeV}$ collected by the STAR detector at RHIC in 2017.Comparisons of the measurements at different energies in $pp$ collisions and $e^{+}e^{-}$ annihilation processes can probe the energy scale dependence and test the universality of the polarizing fragmentation functions.

Speaker: Jinhao He (Shandong University)

spin2025_jinhaohe_slides.pdf

Fundamental symmetries and spin physics beyond the standard model: 03

Conveners: Xu Feng

Conveners: Jian Liang (华南师范大学) , Liuming Liu (Institute of Modern Physics, CAS)

128 Lattice QCD calculation of nucleon EDM

We report our lattice QCD calculation of the nucleon electric dipole moment (EDM) induced by the theta term. We use lattice chiral fermions in our calculation, which provides a fermionic definition of the topological charge exhibiting small discrete effects. Also, the use of chiral fermions guarantees a correct chiral limit even at finite lattice spacings and enables us to reliably extrapolate our result from heavy pion masses to the physical point. With the help of the cluster decomposition error reduction (CDER) technique, we have obtained so far the best results so far for the nucleon EDM.

Speaker: Jian Liang (华南师范大学)

EDM_250924.pdf

129 Accurate B meson and Bottomonium masses and decay constants from the tadpole improved clover ensembles

Using the anisotropic relativistic fermion action on isotropic lattice, we present a systematic study of the masses and lepton decay constants of the mesons with the bottom quark based on the 2+1 flavor tadpole improved clover ensembles at six different lattice spacings from 0.05 to 0.11 fm, various pion masses from 130 to 360 MeV, and several values of the strange quark mass. We also propose a systematic framework to renormalize the quark bi-linear operators with the bottom quark field, and verify it through the renormalized bottom quark mass and decay constants.

Speaker: Dr Mengchu Cai (Institute of Theoretical Physics, Chinese Academy of Sciences)

2_SPIN2025_CaiMengchu_ITP_CAS.pdf

130 Nucleon energy correlators as a probe for light-quark dipole operators at the EIC

In this talk, we propose nucleon energy correlators (NECs) as a novel framework to probe electroweak light-quark dipole operators in unpolarized deep-inelastic scattering. These operators encode chirality-flipping interactions and typically appear quadratically in unpolarized processes. We construct a chiral-odd quark NEC that accesses quark transverse spin via azimuthal asymmetries in the energy flow of the target fragmentation region. We demonstrate that these asymmetries serve as clean and powerful observables for linearly constraining the quark dipole couplings. Unlike existing methods, our approach avoids the need for polarized nucleon beams or particle identification, relying solely on inclusive calorimetric measurements. This work represents one of the first applications of energy correlator observables to new physics searches and offers a robust path to precision studies of chirality-violating effects at the electron-ion collider.

Speaker: Haolin Wang (SCNU)

Spin2025_Haolin.pdf

131 The Production and Decay Dynamics of the Charmed Baryon $\Lambda_c^+$ in $e^+e^−$ Annihilations near Threshold

The study of the charmed baryons is crucial for investigating the strong and weak interactions in the Standard Model and for gaining insights into the internal structure of baryons. In an $e^{+} e^{-}$ experiment the lightest charmed baryon, $\Lambda_c^{+}$, can be produced in pairs through the single photon annihilation process. This process can be described by two complex electromagnetic form factors. The presence of a non-zero relative phase between these form factors gives rise to a transverse polarization of the charmed baryon and provides additional constraints on the dynamic parameters in the decays. In this article, we present the first observation of the transverse polarization of $\Lambda_c^{+}$ in the reaction $e^{+} e^{-} \rightarrow \Lambda_c^{+} \bar{\Lambda}_c^{-}$, based on $6.4 \mathrm{fb}^{-1}$ of $e^{+} e^{-}$annihilation data collected at center-of-mass energies between 4600 MeV and 4951 MeV with the BESIII detector. The decay asymmetry parameters and strong phase shift in the decays $\Lambda_c^{+} \rightarrow p K_S^0, \Lambda \pi^{+}, \Sigma^0 \pi^{+}, \Sigma^{+} \pi^0$ are also simultaneously extracted from the joint angular distributions. These results are vital for understanding $C P$ violation and its role in the matter-antimatter asymmetry of the Universe.

Speaker: Dr Hao Sun (UCAS)

Hao_Sun_UCAS_SPIN2025_Parallel_Talk_0924.pdf

10:00 Coffee/Tea break

132 Exploring Exotic Spin-Dependent Interactions Beyond the Standard Model

New interactions mediated by novel particles propose solutions to several important questions in modern physics.
Axions serve as examples of such particles; they are lightweight and interact weakly with ordinary matter.
This category of particles, including those similar to axions—termed Axion-Like Particles (ALPs)—emerges from diverse theoretical frameworks, including the Peccei-Quinn mechanism addressing the strong CP problem, string theory, and spontaneous supersymmetry breaking.
Given their light mass and weak coupling, ALPs are also possible candidates for cold dark matter.
Introducing these new interactions mediated by novel particles not only tackles several challenges in modern physics but also raises a crucial question: Are there undiscovered interactions beyond the Standard Model?
Many of the interactions predicted by these theories are spin-dependent, which is the primary focus of this review.
In this review, we initially outline the theoretical foundations for investigating exotic spin-dependent interactions, highlighting their importance in various models that go beyond the Standard Model.
We examine the potential roles of new lightweight particles in mediating these interactions, which may enhance our understanding of dark matter.
Relevant formulas derived from theoretical models are included to support experimental investigations.
Following this theoretical framework, we conduct a detailed review of recent experimental efforts aimed at detecting these exotic interactions.
A systematic review of current constraints on these interactions is provided, alongside an assessment of various detection approaches.

Speaker: Haiyang Yan (China Academy of Engineering Physics (CAEP))

haiyangyan_liangrongwu.pptx

133 Measurement of residual μ^+ polarization in a CeF3 material and timing resolution of a CeF3 detector to search for T-violating μ^+ polarization in K^+→π^0 μ^+ ν decay

Time reversal symmetry has long been a subject of interest from pre-modern physics time, since it implies the reversibility of motion. In the K^+→π^0 μ^+ ν (K_μ3) decay, the transverse muon polarization (P_T) is defined as the polarization component perpendicular to the decay plane. A non-vanishing value of P_T provide clear evidence for T-violation under the condition that spurious effects from final state interactions are negligibly small. We are now proposing a new T-violation experiment to achieve ΔP_T~10^(-5) at the J-PARC Hadron Hall without using a magnetic spectrometer. The most important characteristics of the new experiment is the measurements of the muon momentum vector, the π^0 momentum vector, and the muon polarization by the same highly segmented sequential electro-magnetic calorimeter surrounding the K^+ stopping target. Here it should be noted that one of key issues in the experiment is the choice of a scintillation material which can preserve the muon spin polarization for a reasonably long time [1].
A test experiment to measure residual muon polarization in CeF3, LaF3, PrF3, and NdF3 scintillating crystals was performed using a 100% polarized muon beam at J-PARC MLF. In the longitudinal field of 140 Gauss, the muon polarization in these materials was obtained to be 90% at room temperature, which is high enough to perform the new T-violation experiment [1-3]. Since the calorimeter should be placed very close to the K^+ beam line, a single rate for each module will be very high and the timing resolution must be better than 1 ns to reduce accidental background effects. The timing resolution using a CeF3 crystal with the size of 20×20×20 mm^3 was obtained to be ~100 ps using solar-blind phototubes. The time interval of the two CeF3 detector signals generated by the cosmic ray passage was measured. The timing resolution is sufficiently good, and the accidental background must be harmless in the proposed T-violation experiment.
In this talk, some details of the future T-violation experiment, the results of the test experiment to determine the residual polarization in CeF3, LaF3, PrF3, and NdF3 materials and the measurement of the CeF3 timing resolution will be reported.

References
[1] S. Shimizu et al., Nucl. Instrum. Methods A 945 (2019) 162587.
[2] K. Horie et al., Nucl. Instrum. Methods A 1037 (2022) 166932.
[3] Horie et al., Nucl. Instrum. Methods A 1066 (2024) 169606.

Speaker: Mr SHUNGO IDE (The Univesity of Osaka)

spin2025_ide最新.pptx

134 Observation of a family of all-charm tetraquarks with spin-2 and positive parity

We present a detailed spin-parity analysis of near-threshold structures in the fully-charm tetraquark sector, using a matrix-element-based approach applied to the J/\psi J/\psi \rightarrow 4\mu final state. Based on the full Run-2 dataset from the CMS experiment, multiple J^P hypotheses are tested using kinematic distributions of the four-muon system. A set of spin-parity combinations, J^P = 0^+, 0^-, 1^+, 1^-, 2^+, 2^-, is considered. The primary analysis uses decay-only observables, while production angular distributions are also examined to test consistency with a polarized initial state. The result establishes the quantum numbers C = +1, P = +1, and J = 2 as the most likely configuration, offering strong constraints on the nature of fully-charm tetraquark states. Besides, complementary studies with both Run 2 and Run 3 data based on the J/\psi J/\psi and J/\psi \psi(2S) \rightarrow 4\mu final states were also conducted, revealing consistent spectral structures associated with the observed resonances.

Speaker: Xining Wang (IHEP)

7_spin_wangxining.pptx

135 Covariant L-S decomposition by spinor variable

In high-energy physics, traditional spin-orbit (L-S) decomposition effectively describes 3-point interaction structures and fully characterizes 3-point kinematics. However, its formulation is entirely dependent on the Center-of-Mass Frame (CMF) angular variables $(\theta,\varphi)$, necessitating Lorentz boosts back to the CMF for decomposition in practical calculations, which adds complexity.​ To resolve this, we use covariant spinor variables to construct a formally covariant spin-orbit coupling. This formulation enables L-S decomposition of amplitudes in any arbitrary reference frame, eliminating the requirement to return to the CMF and streamlining spin-dependent analyses. Furthermore, leveraging this tool, we can establish the general structure of Form Factors, construct covariant spin-operators, and develop covariant tomography for high-energy interaction analyses.

Speaker: Mr Yi-Ning Wang (ITP)

8_CovariantLLSdecompositionbyspinor.pdf

Future facilities and experiments

Conveners: Pasquale Di Nezza, Bill Wenliang Li

Convener: Yuji Goto

136 [Cancelled] Exploring Short-Range Correlations (SRC) in Nuclei through Hadronic Probes at JINR

Short-Range Correlations (SRC) emerge when a proton and neutron within a nucleus come into close proximity - at distances comparable to the nucleon radius - forming a high-momentum, strongly interacting pair. This phenomenon offers a unique window into the transition region between two descriptions of nuclear matter: the low-resolution picture of nuclei as systems of protons and neutrons, and the high-resolution view governed by quark and gluon degrees of freedom.

Over the past decade, electron scattering experiments have established SRCs as a key feature of nuclear structure, influencing nucleon-nucleon interactions, nuclear binding, and many-body dynamics. Building on these insights, the Joint Institute for Nuclear Research (JINR, Russia) has initiated a dedicated program to study SRCs via hadron-hadron interactions, providing complementary information to that obtained from electron scattering.

This program employs GeV/nucleon-energy ion beams impinging on a cryogenic liquid hydrogen target, optimized for probing SRCs through hard quasi-elastic knockout reactions in inverse kinematics. These reactions selectively probe single nucleons or correlated nucleon pairs with high internal momenta and allow reconstruction of nuclear fragments and their momentum distributions. Following two successful experimental runs with a carbon-12 beam, the next phase, reported here, will utilize a tensor-polarized deuteron beam, aiming to unravel spin-dependent aspects of SRC dynamics and deepen our understanding of the underlying nuclear forces.

Speaker: Maria Patsyuk (Joint Institute for Nuclear Research)

137 ePIC at the upcoming EIC

The Electron-Ion Collider (EIC), scheduled to commission in the early 2030s, will be the world’s first facility that collides a polarized electron beam with a polarized proton beam as well as ion beams. The collider will be built at the Brookhaven National Lab (BNL). The Electron-Proton/Ion Collider (ePIC) is a general purpose detector to be built at the six-o’clock interaction point (IP6) of the accelerator ring. With EIC’s high luminosity beams and the 4$\pi$ coverage of the detector setup, ePIC will be able to take large statistics polarized scattering measurements over a wide range of kinematics including regions that have not yet been explored. The detector is designed to answer many important and long-existing questions in nuclear physics, including the spin crisis of proton, origin of nucleon mass and gluon saturations. In this presentation, an overview of the ePIC detector system will be given, and highlights of the potential science programs will be discussed.

Speaker: Win Lin (Stony Brook University)

SPIN 2025 ePIC - small.pdf

138 Projected High Precision Measurements on the Spin Structure g1 at EIC

The spin structure function $g_1$ is important for understanding the quark spin contribution to the overall spin of nucleons, which has been a long standing puzzle in nuclear physics. Through the $Q^{2}$ dependence of $g_1$, the structure function is also sensitive to the gluon spin contribution. In addition, it is important for testing the Bjorken sum rule and can provide a unique way of obtaining the strong coupling constant. $g_1$ can be measured via the longitudinal and transverse double spin asymmetry in polarized deep inelastic scattering, which has been tested at various fixed target experiment in the past. However, to better address the current opened QCD questions as raised earlier, polarized data with wider kinematic coverage reaching low $x$ and high $Q^2$ region are needed. The ePIC detector at the future Electron Ion Collider aims to measure high precision $g_1^p$ and $g_1^n$ from $ep$ DIS and $e^{3}\rm{He}$ DIS uncovering a large fraction of this previously unexplored area. The details of the experiment and measurement methods will be discussed in this presentation, along with a quantitative projected results estimated using the latest detector simulation and analysis.

Speaker: Win Lin (Stony Brook University)

SPIN2025 g1.pdf

139 An overview of the upcoming MOLLER experiment at Jefferson Lab

The upcoming MOLLER (Measurement Of Lepton Lepton Electroweak Reaction) experiment at Jefferson Lab aims to measure parity violation in fixed-target electron-electron scattering with unprecedented precision and significantly extend the reach for new dynamics beyond the Standard Model in the electroweak sector. Using the high-intensity, high-precision 11 GeV electron beam at Jefferson Lab, MOLLER proposes to measure the parity-violating asymmetry in the scattering of longitudinally polarized electrons off unpolarized electrons to an overall fractional accuracy as high as 2.4%. Fabrication of the novel spectrometer and detector systems is already well underway, and the experiment is targeting its first physics run in early 2027. This talk will provide a brief overview of the experimental goals as well as experimental techniques and key features of detector subsystems that are critical to achieving the stringent accuracy requirements of the MOLLER experiment.

Speaker: Nguyen Huong (University of Virginia)

HuongNguyen_UVa_MOLLER_SPIN2025.pdf

10:00 Coffee

140 Detector development for EicC at HIAF

The proposed Electron-Ion Collider in China (EicC) envisions advancing China's future High-Intensity heavy-ion Accelerator Facility (HIAF) through strategic upgrades to establish a polarized electron-ion collider. This premier facility will provide a comprehensive experimental platform for nuclear physics, particle physics, and related scientific disciplines in China. Functioning as a modern analogue to Rutherford scattering experiments, the electron-ion collider represents an unparalleled instrument for probing the deep structure of matter. This report details EicC's primary physics goals alongside current progress in detector system design and R&D initiatives.

Speaker: Aiqiang GUO (Institute of modern physics, Chinese Academy of Sciences)

Introduction_EicC - guoaq.pdf

141 Hyperon-Nucleon Spectrometer at HIAF

Hyperons were found to be polarized in p-Be collisions at Fermilab as early as 1976, 12 years before the EMC results sparked the "proton spin crisis." Since then, polarized Lambda hyperons have been observed in electron-positron, proton-proton, and proton-ion collisions. However, unlike the extensive study of nucleon spin structure, the origin of Lambda polarization lacks systematic investigation, both theoretically and experimentally. Starting in 2026, the High Intensity heavy-ion Accelerator Facility (HIAF) in Huizhou, China, will deliver high-intensity proton beams (up to ~10 GeV) and various ion beams. This talk presents a proposal for a Hyperon-Nucleon Spectrometer at HIAF, designed to perform multi-dimensional mapping of Lambda polarization in fixed-target p-p, p-A, and A-A collisions.

Speaker: Yuxiang Zhao (Institute of Modern Physics, Chinese Academy of Sciences)

6_Yuxiang_HNS-September-Spin-conference.pdf

142 The progress of Super Tau Charm Facility in China

The proposed STCF is a symmetric electron-positron beam collider designed to provide e+e− interactions at a centerof-mass energy from 2.0 to 7.0 GeV. The peaking luminosity is expected to be 0.5×10^35 cm−2s−1. STCF is expected to deliver more than 1 ab−1 of integrated luminosity per year. The huge samples could be used to make precision measurements of the properties of XYZ particles; search for new sources of CP violation in the strange-hyperon and tau−lepton sectors; make precise independent mea-surements of the Cabibbo angle (theta)c) to test the unitarity of the CKM matrix; search for anomalous decays with sensitivities extending down to the level of SM-model expectations and so on. In this talk, the physics interests will be introduced as well as the  the recent progress on the project R&D.

Speakers: Haiping Peng, Zhujun Fang (USTC)

20250924 The progress of Super%0D%0A Tau Charm Facility in China.pdf

143 Spin physics at HIAF

The High Intensity heavy-ion Accelerator Facility (HIAF) will be a major workhorse for the accelerator-based (sub)atomic physics in the multi-GeV region in the next decades. As fundamental as the mass, spin plays a profound role in the structure of microscopic particles and interactions among them. Besides, spin has long provided unique approaches to test fundamental symmetries and to search for new physics beyond the Standard Model of particle physics.

In order to extend the discovery potential of HIAF in the fields of spin-dependent dynamics/structure and symmetry tests, developments of tools for spin-polarized experiments, such as polarized ion sources, acceleration of polarized beams and beam polarimetry, are currently ongoing. A variety of experiments with processes $p\vec{p}$, $p\vec{e}$, $A\vec{e}$, $A\vec{d}$ at different scales, ranging from atomic physics, over nuclear physics, down to hadron physics, can be performed at HIAF. This talk will discuss a few highlighted physical programs and related R&D activities.

Speaker: Boxing Gou (Institute of Modern Physics, CAS)

SPIN2025_Gou.pdf

Nucleon helicity structure: 03

Conveners: Matthew Posik, Raza Sabbir Sufian, Jinlong Zhang

Convener: Craig Roberts (Nanjing University)

144 Proton spin structure from a light-front Hamiltonian approach

I will report our recent results on proton spin structure from a light-front Hamiltonian approach. In this approach we obtain the light-front wave function of the proton through solving the eigenvalue problem of the light-front Hamiltonian of QCD in a basis based on the Fock-sector expansion. Then using the obtained light-front wave function we calculate the observables characterizing the spin structure of the proton. I will present our results on spin-dependent collinear, generalized and transverse-momentum-dependent parton distributions for the quarks and gluons in the proton. Based on these observables I will show the resulting proton spin decomposition from the light-front Hamiltonian viewpoint.

Speaker: Xingbo Zhao (Institute of Modern Physics, Chinese Academy of Sciences)

Spin2025_250922_siqi_final.pdf

145 Six-dimensional light-front Wigner distributions of the proton

Our study, rooted in hadron physics, addresses the incomplete information limitation of traditional parton distribution functions. We investigate the six-dimensional (6D) light-front Wigner distribution function of the proton (a spin-1/2 hadron) using the 6D light-front Wigner distribution framework constructed by our team.

At the leading twist, 16 independent distribution functions accounting for different polarizations are defined; their integration results carry specific physical meanings. The 6D light-front Wigner distribution features a quasi-probability nature: integration enables generation of known observables and definition of new low-dimensional distribution functions for exploring novel physical phenomena.

Employing the spectator model for proton Wigner distribution calculations, numerical results show the 6D Wigner distribution exhibits centrosymmetry or dipolar symmetry in specific planes, with function values generally increasing alongside relevant parameters. Qualitative analysis is also conducted on physical quantities like intrinsic orbital angular momentum.

Speaker: Yirui Yang (Peking Uniersity)

yyr-Qingdao.pdf

146 The nucleon structure from an AdS/QCD model in the Veneziano limit

We employ the VQCD model, a holographic approach that dynamically simulates essential QCD characteristics, including linear mass spectra, confinement, asymptotic freedom, and magnetic charge screening, while incorporating quark flavor effects. Using this model, we first calculate the proton mass spectrum and the wave function, incorporating anomalous dimensions to refine our
results. Next, we compute the proton structure functions across a range of Bjorken x values using consistent parameters. Furthermore, we derive the proton electromagnetic form factor by solving the equation of motion for electromagnetic field, accounting for background effects, and demonstrate
qualitative consistency with results from free electromagnetic fields coupled to fermions. Finally, we calculate the gravitational form factors by introducing an effective graviton mass m arising from
chiral symmetry breaking and the proton energy-momentum tensor. Our calculations yield results that are in excellent agreement with experimental data and lattice QCD computations, validating the VQCD model as a robust tool for studying proton properties.

Speaker: Defu Hou (CCNU)

Defu Hou-NucleonStructure-spin2025.pdf

147 Measurement of the transverse momentum dependent(TMD) longitudinal single-spin asymmetries of W boson at RHIC-STAR

Understanding the three-dimensional spin structure of the nucleon is one of the key questions in QCD. Among the transverse-momentum-dependent (TMD) PDFs, the TMD helicity distributions in particular are poorly constrained. Measurements of the longitudinal single-spin asymmetry ($A_L$) of $W^\pm$ bosons in polarized proton-proton collisions at RHIC provides a unique opportunity for accessing the flavor separated TMD helicity distributions of quarks and anti-quarks. The $W^\pm$ bosons can be identified through their leptonic decay channel ($W \rightarrow e + \nu$), and their full kinematics can be constructed by using a recoil-based method. In this talk, we will present the motivation, analysis procedures, and the status of the $A_L$ measurement as functions of $W^\pm$ transverse momentum and rapidity, based on the dataset collected by the STAR experiment in longitudinally polarized $p+p$ collisions at $\sqrt{s} = 510~\mathrm{GeV}$ in 2013.

Speaker: Chao Wang (Shandong University)

SPIN2025_chao.pdf

Spin in heavy ion collisions

Conveners: Enrico Speranza, Jinhui Chen, Takafumi Niida

Conveners: Jinfeng Liao (INDIANA UNIVERSITY &amp; RBRC) , Qun Wang (University of Science and Technology of China)

148 Relativistic spin hydrodynamics and spin polarization

Recent experimental success of detecting the spin polarization of Lambda hyperons in heavy-ion collisions enables us to extract the novel properties of fluid vorticity and spin transport of quark gluon plasma (QGP). These findings motivated the development of a hydrodynamics-like theory for spin polarization and transport. We will discuss the construction of such a theory (the relativistic spin hydrodynamics) and how it can be applied to heavy-ion collisions. We will also discuss possible extension of the spin hydrodynamics to include dilation current.

Speaker: Xu-Guang Huang (Fudan University)

x.g.huang-2025.09.24.pdf

149 Hydrodynamic study of Lambda spin polarization: from qualitative towards quantitative investigation

The “local Lambda polarization puzzle” in relativistic heavy-ion collisions has challenged conventional models based solely on thermal vorticity, which fail to reproduce the observed sign of local polarization. Recently, incorporating shear-induced polarization (SIP) successfully reproduces the sign and opens the path toward a quantitative description of spin polarization.

Using 3+1D MUSIC with AMPT initial conditions and the “strange memory scenario,” we show that global and local Lambda polarization in 200 GeV Au+Au and 5.02 TeV Pb+Pb collisions are well described. The same framework also predicts system-size–independent signals in 200 GeV Ru/Zr isobar collisions, consistent with STAR results. At RHIC Beam Energy Scan energies, we further identify a baryonic spin Hall effect: baryon chemical potential gradients induce Lambda/anti-Lambda local polarization splitting. Simulations with AMPT, SMASH, and 3D Glauber initial conditions predict growing signals at lower energies, in agreement with recent BES-II measurements.

Speaker: Baochi Fu (Peking University)

BaochiFu_SPIN2025v2.pdf

150 Physics-informed neural networks for angular-momentum conservation in computational relativistic spin hydrodynamics

Theoretical developments in relativistic spin hydrodynamics, which explicitly describes the internal angular momentum of a fluid element as spin, have progressed rapidly since the experimental observation of the global spin polarization of Λ hyperons in relativistic heavy-ion collisions. However, numerical simulations of relativistic spin hydrodynamics remain underdeveloped due to significant computational challenges, one of which is the accurate preservation of angular-momentum conservation.

In this work, we demonstrate the application of physics-informed neural networks (PINNs), a neural-network-based learning framework, to simulations of relativistic spin hydrodynamics, as has been done for non-relativistic hydrodynamics. We highlight the flexibility of PINNs, which allows angular-momentum conservation to be imposed as a penalty in the training process. As a proof of concept, we consider a rotating fluid confined in a cylindrical container.

We first show that angular-momentum conservation can be accurately preserved by incorporating it into the loss function. We then numerically investigate the role of the rotational viscous effect in driving the conversion between orbital and spin angular momentum.

Speaker: Hidefumi Matsuda (Fudan University)

SPIN2025_HM.pdf

151 Relativistic spin hydrodynamics with antisymmetric spin tensors and an extension of the Bargmann-Michel-Telegdi equation

We derive a formulation of relativistic spin hydrodynamics with totally antisymmetric spin tensors that satisfy the Frenkel-Mathisson-Pirani condition. In our proposed spin hydrodynamics, the second law of thermodynamics is fulfilled by the spin-induced corrections in the heat flow, the viscous tensor, and the antisymmetric part of the energy-momentum tensor. These corrections are interpreted as the inverse spin Hall effect and the anomalous Hall effect in the nonrelativistic limit. We show that our evolution equation for the spin density is interpreted as an extension of the Bargmann-Michel-Telegdi equation known in relativistic many-body systems, including the Thomas precession term, the spin-rotation term, and new coupling terms between spin and hydrodynamic variables.

Speaker: Mr Dong-Lin Wang (中国科学技术大学)

DongLinWang_250924.pdf

10:00 Coffee break

152 Relativistic dynamics of charmonia in strong magnetic fields

In this talk, I present our recent investigation of charmonium systems in strong external magnetic fields using a relativistic light-front Hamiltonian approach within the basis light-front quantization (BLFQ) framework. By solving the eigenvalue problem for the invariant mass squared operator — incorporating confinement potentials and one-gluon-exchange interactions — we compute the mass spectrum and wave functions across varying magnetic field strengths. Our results reveal significant spectral modifications driven by the Zeeman effect, including $\eta_c$-$J/\psi$ mixing and splitting of magnetic sublevels. Analysis of the momentum density distributions shows pronounced wave function deformation: transverse momentum broadening and longitudinal compression in strong fields, along with notable structural changes in parton distribution profiles — such as the emergence of double-hump structures in excited states. We find that relativistic corrections and center-of-mass coupling play a crucial role in these dynamics, underscoring the necessity of a fully relativistic treatment for accurately describing QCD bound states in extreme electromagnetic environments and vorticity.

Speaker: Yang Li (University of Science and Technology of China)

YangLi_Spin2025_Sept2025.pdf

153 String tension and Polyakov loop in a rotating background

We study the influence of a rotation on the string tension and the temperature of the confinement-deconfinement phase transition of gluodynamics by gauge/gravity duality. We explore two distinct approaches, global transformation and local transformation, to introduce rotation and compare the results. It is shown that the string tension extracted from the free energy in the presence of a heavy quarkonium
decreases with increasing angular velocity, while the transition temperature determined by the Polyakov loop increases with increasing angular velocity, which is in line with lattice simulations.

Speaker: Jun-Xia Chen (华中师范大学)

Jun-Xia Chen Spin.pdf

154 Rapidity-Spectral Decomposition and Spin Dynamics in Coupled Lorentz Spacetime Coordinates

We present a novel framework for parameterizing Lorentz spacetime coordinates using coupled rapidity parameters, extending classical special relativity with new insights into rapidity symmetries and spin effects. Building upon the Euler–Hamilton formalism, we introduce angular and transverse rapidities, enabling spectral decompositions of relativistic dynamics into elementary functions even when explicit analytic solutions are unavailable. A limiting process is developed to achieve this decomposition, providing new tools for modeling complex relativistic systems. We further expand the relativistic Hamiltonian and Lagrangian into rapidity spectra, yielding a new class of Lorentz coordinates with explicit rapidity dependence. These coordinates are applied to analyze charged particle dynamics in the fields of both plane monochromatic waves and pulsed laser beams. The kinetic energy and trajectory differences arising from the use of classical, rapidity-based, and Fermi-type coordinates are compared in detail. As a key advancement, we incorporate spin degrees of freedom into the rapidity-parametrized formalism. By coupling spin precession equations (via the Bargmann–Michel–Telegdi formalism) with rapidity variables, we derive new spin evolution equations for relativistic particles in 3+1 dimensions. The impact of the new spacetime parametrization on spin-orbit interactions and helicity conservation is analyzed. We also explore the structure of the proper Lorentz group SO(1,3) with coupled parameters, comparing transformations in old, new, and Fermi coordinates. Finally, as a special case, we demonstrate the applicability of our formalism to 1+1 dimensional relativistic hydrodynamics with spin, opening a path toward modeling spin-polarized relativistic fluids. These results contribute to the broader understanding of spin dynamics in high-energy particle and laser–plasma physics.

Speaker: Nikolai Akintsov (Nantong University)

Akintsov N.pptx

155 Global Spin Alignment of (Anti-)4Li in Non-Central Heavy-Ion Collisions

Non-central heavy-ion collisions produce hot and dense nuclear matter with significant fluid vorticity, which induces global polarizations of particles with non-zero spins along the direction of the total orbital angular momentum. This phenomenon has been observed for hyperons and vector mesons in experiments. In the present study, we demonstrate that polarized nucleons lead to global spin alignment of the unstable nucleus 4Li, which decays via 4Li → 3He + p. Assuming 4Li formed through the coalescence of polarized nucleons at kinetic freeze-out, we obtain the angular distribution of the daughter particle 3He. The quantum corrections up to ℏ2 in the coalescence calculation is included through the Moyal star product. We find that the angular distribution has a cos(2θ∗) dependence, where θ∗ is the angle of the daughter particle 3He in the rest frame of 4Li with respect to the quantization axis. We also find that it depends on both the vorticity and the polarization of nucleons at the kinetic freeze-out stage. Future measurements on the spin alignment of 4Li thus offer a promising method to probe the spin dynamics and vortical structure of nuclear matter produced in heavy-ion collisions.

Speaker: Yunpeng Zheng

Global spin alignment of Li4 final edition.pdf

156 Global tensor polarization of spin-3/2 hadrons and quark spin correlations in relativistic heavy-ion collisions

The STAR Collaboration results on global spin alignment of vector mesons in heavy-ion collisions [1] reveal that quarks in the quark-gluon plasma (QGP) exhibit not only global polarization[2, 3] but also spin correlations, leading the study on spin effects in heavy-ion collisions to a new climax.

A systematic formalism for describing spin correlations in a system of spin-1/2 particles and their relationships to experimental observables is given in Ref.[4]. This framework is further extended in Ref.[5] to compute the global polarizations of spin-3/2 baryons in relativistic heavy-ion collisions. The calculation results show that the rank-2 and rank-3 tensor polarizations of spin-3/2 baryons reflect local two and three quark spin correlations respectively. A more comprehensive set of results will be published in a forthcoming paper[6].

This report aims to present the relationships between measurable spin-3/2 baryon tensor polarization and quark spin correlations, explore methods to extract these correlations from measurements of successive spin-3/2 baryon decays.

References
[1] M. S. Abdallah et al. [STAR], “Pattern of global spin alignment of ϕ and K∗0 mesons in heavy-ion
collisions,” Nature 614, 244 (2023).
[2] Z. T. Liang and X. N. Wang, “Globally polarized quark-gluon plasma in non-central A+A collisions,”
Phys. Rev. Lett. 94, 102301 (2005).
[3] Z. T. Liang and X. N. Wang, “Spin alignment of vector mesons in non-central A+A collisions,”
Phys. Lett. B 629, 20 (2005).
[4] J. p. Lv, Z. h. Yu, Z. t. Liang, Q. Wang and X. N. Wang, “Global quark spin correlations in
relativistic heavy ion collisions,” Phys. Rev. D 109, 114003 (2024).
[5] Z. Zhang, J. p. Lv, Z. h. Yu and Z. t. Liang, “Global tensor polarization of spin 3/2 hadrons and
quark spin correlations in relativistic heavy ion collisions,” Phys. Rev. D 110, 074019 (2024).
[6] J. p. Lv, Z. h. Yu, Z. t. Liang, “The complete results of global polarization and spin correlation of
hadrons with different spins in relativistic heavy ion collisions,” paper in preparation.

Speaker: Zihan Yu (Shandong University)

SPIN2025俞子涵v3.pdf

Quantum computing and artificial intelligence: 01

Conveners: Kai Zhou, Longgang Pang

Convener: Yao Ji

157 Quantum simulations of non-perturbative quantities in hadron scattering

In this presentation, I will discuss our exploratory work on simulating non-perturbative QCD quantities relevant to hadron scattering processes using quantum computing methods. This includes mapping lattice gauge field theories to qubits, simulating parton distribution functions (PDFs), Light-cone distribution amplitudes, and Fragmentation functions on a quantum computer.

Speaker: Tianyin Li (RIKEN)

2025_09_24_spin.pdf

158 [Cancelled] Quantum computing of chirality imbalance in SU(2) gauge theory

We implement a variational quantum algorithm to investigate the chiral condensate in a 1+1 dimensional SU(2) non-Abelian gauge theory. The algorithm is evaluated using a proposed Monte Carlo sampling method, which allows the extension to large qubit systems. The obtained results through quantum simulations on classical and actual quantum hardware are in good agreement with exact diagonalization of the lattice Hamiltonian, revealing the phenomena of chiral symmetry breaking and restoration as functions of both temperature and chemical potential. Our findings underscore the potential of near-term quantum computing for exploring QCD systems at finite temperature and density in non-Abelian gauge theories.

Speaker: Guofeng Zhang (South China Normal University)

159 hadronic tensor in (1+1)-dimensional systems by quantum computing

The hadronic tensor encodes key information about the internal structure of hadrons, reflecting the non-perturbative features of quantum chromodynamics (QCD). We perform a direct computation of the hadronic tensor in (1+1)-dimensional $U(1)$ and $SU(2)$ gauge theories by evaluating the real-time current-current correlation function using proposed quantum algorithms implemented on classical hardware. We demonstrate that the elastic form factor can be reliably extracted from the hadronic tensor, with results showing good agreement with those obtained via exact diagonalization.

Speaker: Dairui Zou (South China Normal Universi)

20250924_Qindao_DZ.pdf

Low energy spin physics with lepton, photon and hadron probes: 01

Conveners: Chao Peng, Tom Jude

Convener: Weizhi Xiong (Shandong University)

160 Experiments at MAMI/MESA

This talk will present the current status of experiments using polarized electrons at the accelerator facilities MAMI and MESA in Mainz. A particular focus will be on the P2 experiment, which aims to precisely determine the weak mixing angle at low momentum transfer. This measurement provides a stringent test of the Standard Model and offers sensitivity to potential new physics at energy scales up to approximately 50 TeV.

Speaker: Sebastian Baunack (JGU Mainz)

Baunack_Spin2025.pdf

161 Electroweak precision test through single spin asymmetries at the EicC

Parity played a very important role in the development of the Standard Model (SM), as well as subsequent precision tests of the latter through a determination of the weak mixing angle. The longitudinal beam polarization of the proposed Electron-ion collider in China (EicC) offers a new possibility in this regard, and in a regime unexplored before. In this talk and based on our recent work, I will discuss how EicC helps in SM precision tests through the single spin asymmetries.

Speaker: Yong Du (IMP CAS)

SPIN2025-YongDu.pdf

162 Cosmic Ray Muon Polarization to Facilitate Atmospheric Neutrino Physics

Atmospheric neutrinos (ATNs) offer a paradigm to understand neutrino properties while it is critical to quantify uncertainties in the flux modelings. Measurement of cosmic ray muons will contribute to the precision measurement of atmospheric neutrino oscillations due to the same parent particles. This letter suggests measuring the polarization of cosmic ray muons with an array strategy good for understanding low-energy cosmic ray muons and atmospheric neutrinos. Constraints on long-standing atmospheric neutrino flux uncertainties in the few-GeV range are achievable within one year using a $\mathcal{O}(10) \mathrm{m}^2$ array of Cosmic-Ray muon Spin polarization detectoRs (CRmuSRs).

Speaker: Ming-Chen Sun (Sun Yat-sen University)

25MingchenSun_CRmuSR.pdf

Lunch

Excursion

Banquet

Thursday, 25 September

Plenary

Conveners: Viktor Fimushkin (JINR) , Xin-Nian Wang (Central China Normal University)

163 Polarized fusion

Speaker: Ralf Engels (Forschungszentrum Jülich)

Polarized Fusion.pptx

164 Dubna, polarized targets, history and plans

Speaker: Anton Dolzhikov (JINR)

DolzhikovAS_SPIN2025_Dubna PT.pdf

09:50 Coffee break

165 Heavy ion spin experiments

Speaker: Takafumi Niida (University of Tsukuba)

SPIN2025-niida.pdf

166 Heavy ion spin theory

Speaker: Francesco Becattini (Università di Firenze)

becattini.pdf

167 Chiral magnetic effect

Speaker: Jinfeng Liao (INDIANA UNIVERSITY &amp; RBRC)

LIAO_SPIN2025.pdf

Lunch

Plenary

Conveners: Shunzo Kumano (IMP / KEK) , Guo-Liang Ma (Fudan University)

168 TMD theory

Speaker: Kazuhiro Watanabe (Tohoku University)

SPIN2025_Watanabe.pdf

169 Drell-Yan spin physics

Speaker: Wen-Chen Chang (Institute of Physics, Academia Sinica)

SPIN2025_DrellYanSPIN_wchang.pdf

15:20 Coffee break

170 GPD theory

Speaker: Paweł Sznajder (National Centre for Nuclear Research, Poland)

sznajder_0925.pdf

171 Lattice calculation of GPDs

Speaker: Huey-Wen Lin (M)

hwlin_Spin2025.v3.pdf

172 Proton charge radius

Speakers: Ashot Gasparian (North Carolina A&T State University) , Haiyan Gao (Duke University)

Proton-Charge-Radius-Spin2025.pdf

Friday, 26 September

Plenary

Conveners: Qun Wang (University of Science and Technology of China) , Xu-Guang Huang (Fudan University)

173 SoLID and Future Programs at JLab

Speaker: Haiyan Gao (Duke University)

Spin-2025-SoLID-HGao.pdf

174 NICA SPD project

Speaker: Alexey Guskov (JINR)

SPD_spin_2025_v2.pdf

09:50 Coffee break

175 EIC status

Speaker: Bernd Surrow (Temple University)

BSurrow-SPIN2025_EIC_Status.pdf

176 From HIAF to EicC

Speaker: Jiancheng Yang (IMP CAS)

From HIAF to EicC-Jiancheng Yang.pdf

From HIAF to EicC-Jiancheng Yang.pptx

177 The LHCSpin project

A polarized gaseous target, operated in combination with the high-energy and high-intensity LHC beams, has the potential to open new physics frontiers and to deepen our understanding of the strong interaction in the non-perturbative regime of QCD. Specifically, the LHCspin project aims to perform spin-physics studies in high-energy polarized fixed-target collisions using the LHCb detector. Being designed and optimized for the detection of heavy hadrons, LHCb will allow to probe the nucleon structure through, e.g., the inclusive production of c- and b-hadrons, and ideal tool to access the essentially unexplored spin-dependent gluon TMDs. This configuration will allow to explore the nucleon internal dynamics at unique kinematic conditions, including the poorly explored high x-Bjorken and high x-Feynman regimes. With the installation of the proposed setup, LHCb will become the first experiment delivering simultaneously unpolarized beam-beam collisions at 14 TeV and both polarized and unpolarized beam-target collisions at center-of-mass energies of the order of 100 GeV. The current status of the LHCspin project is presented, with a focus on the anticipated timeline for its experimental implementation.

Speaker: Shankar Rahul (University of Ferrara and INFN)

SPIN2025_LHCspin_2.pptx

Lunch

Plenary

Conveners: Yi-Bo Yang (ITP/CAS) , Yi Liao (IQM, South China Normal University)

178 Small-x spin physics

Speaker: Bowen Xiao (The Chinese University of Hong Kong (Shenzhen))

SPIN2025.pdf

179 Quantum computing

Speaker: Hideki Okawa (IHEP CAS)

okawa_SPIN2025_QC_20250926.pdf

15:20 Coffee break

180 Latest Results from the Muon g-2 Experiment at Fermilab

The muon magnetic anomaly, $a_\mu = (g-2)/2$, can be both measured and computed to a very high precision, making it a powerful probe to test the Standard Model of particle physics and search for new physics. The Fermilab Muon g-2 Collaboration has recently released the third and final measurement of the magnetic anomaly of the positive muon. The measurement shows excellent agreement with the previous measurements and with the previous E821 experiment at Brookhaven (USA). The final record-breaking precision of 127 parts per billion (ppb) surpassed the initial design goal of the experiment. This achievement was possible thanks to both high statistics and to the extensive and scrupolous analysis of the magnetic fields, the beam dynamics, and the particle detection, obtaining a final systematic uncertainty under 80 ppb. This talk will cover the highlights of the latest measurement, discuss its comparison with the latest Standard Model predictions, and provide an outlook on the upcoming analyses.

Speaker: Paolo Girotti (INFN - Laboratori Nazionali di Frascati)

pgirotti_SPIN2025_g-2_nogif.pdf

181 Search for Electric Dipole Moments and Axions/ALPS with Polarized Hadron Beams in Storage Rings

The research addresses two fundamental questions in particle physics and cosmology: the fate of antimatter after the Big Bang and the nature of Dark Matter (DM). Its focus lies on the study of Electric Dipole Moments (EDMs) in particles such as protons and deuterons, explored through polarized particle beams stored in a dedicated ring.

Up to now, experimental efforts have been carried out at the COoler SYnchrotron (COSY) storage ring at Forschungszentrum Jülich in Germany, which ceased operations at the end of 2023. The next step foresees the design and construction of a Prototype Storage Ring (PSR), in both all-electric and hybrid (electric and magnetic) configurations, operating at beam energies of 30–45 MeV with a circumference of about 100 meters. The PSR will serve as a testbed to resolve key technical challenges and pave the way toward a full-scale EDM facility dedicated to precise proton EDM measurements.

In the subsequent phase, a high-precision EDM facility with 233 MeV beam energy and a circumference of approximately 500 meters will be developed. This installation is expected to push the current sensitivity limits of the neutron’s static EDM to unprecedented levels, potentially enabling groundbreaking discoveries in our understanding of the fundamental symmetries of nature.

Speaker: Paolo Lenisa (University of Ferrara and INFN)

LENISA_ISPC.pdf

LENISA_SPIN2025_25_09_26.pdf

182 Baryon CP violation measurement

Speaker: Yanxi Zhang (Peking University)

LHCbBaryonCPV.pdf

LHCbBaryonCPV.pptx

183 Closing remark

LENISA_ISPC.pdf