17th International Conference on Heavy Quarks and Leptons (HQL 2025)

15 Sep 2025, 08:00 → 19 Sep 2025, 18:00 Asia/Shanghai

Conference Overview

The XVII International Conference on Heavy Quarks and Leptons (HQL 2025) will be held at Peking University, Beijing, China during September 15-19, 2025.

The Heavy Quarks and Leptons conference series is dedicated to the study of heavy quarks, namely charm, bottom, and top, with possible extensions to interesting topics involving the strange quark. Neutrino oscillation studies as well as new insights into the muon and tau lepton sectors are also included. It continues the tradition of regular scientific meetings, first started in 1993 at the Laboratori Nazionali di Frascati under the name "Heavy Quarks at Fixed Target", and widened in 2002 to include leptons, with the workshop being renamed to its current form.

This marks the hosting of the HQL Conference in China for the first time. We sincerely hope all participants will not only engage in fruitful academic exchanges, but also immerse themselves in the profound richness of Chinese culture during this gathering.

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Key information

• Dates: 15-19 September 2025 (Asia/Shanghai timezone)
• Location: Beijing, China
• Host Institutions: Peking University & University of Chinese Academy of Sciences
• Organizers: Liupan An (PKU), Jinlin Fu (UCAS), Xiaohu Sun (PKU), Yanxi Zhang (PKU), Chen Zhou (PKU)
• Supported by: State Key Laboratory of Nuclear Physics and Technology & Center for High Energy Physics, Peking University & National Natural Science Foundation of China (NSFC)

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Topics to cover

• Neutrino Physics
• Precision Lepton Measurements
• Spectroscopy
• Kaon Physics
• Top Quark Physics
• CP Violation
• Rare Decays
• CKM Matrix
• New Experiments

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Important Dates

• Early registration deadline: 20 July 2025 
• Registration close: 20 August 2025
• HQL2025 Conference:  15-19 September 2025

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Contact

hql2025-Beijing@pku.edu.cn

For real-time communication, please scan the QR code below to join the HQL2025 WeChat group:

For_Chinese_participants_会议证明.pdf

For_Chinese_participants_会议通知.pdf

group_photo.jpg

Poster-HQL2025.png

Monday, 15 September

1 Registration

Opening Speech

Convener: Zhenwei Yang (Peking University, Beijing, China)

Hot topics

Convener: Bingsong ZOU (ITP, CAS)

2 CPV in baryons (results from LHCb, BESIII)

Speaker: Shanzhen Chen (高能所（IHEP, CAS）)

Shanzhen_CPVinbaryon_v4.pdf

3 Status of muon g-2 theory

Speaker: Finn McInnes Stokes

finnstokes_hql2025.pdf

4 Final measurement with 0.12 ppm precision from the Muon g-2 Experiment at Fermilab

The Fermilab Muon g-2 experiment has measured the muon's anomalous magnetic moment (a_μ) with a precision of 139 ppb, based on Run-456 dataset collected from 2020 to 2023. The new result confirms the earlier Run1 and Run2-3 measurements while significantly reducing overall uncertainty through improved systematic controls and using over 2.5 times more positron statistics than before. The combined Fermilab measurement yields a value of a_μ(exp, FNAL)=1165920705(148)×10⁻¹²(127 ppb), improving the experimental precision on the world average value by more than a factor of four. This talk will highlight the final dataset’s analysis methods and systematic control strategies, include a comparison with the latest Standard Model prediction, and finally offer a brief outlook on the Muon g-2/EDM experiment planned at J-PARC.

Speaker: Bingzhi Li (Zhejiang Lab 之江实验室)

Fermilab Muon g-2.pptx

5 Search for entanglement effects at high energies

(including top pair production at threshold and topomium)

Speaker: Carmen Diez Pardos

Entanglement_CDiezPardosHQL2025.pdf

10:30 Group photo

10:35 Coffee break

Spectroscopy

Convener: stefano bianco (高能所)

6 Theoretical review on light meson and heavy hadron spectroscopy

Speaker: Qiang ZHAO (Institute of High Energy Physics, Chinese Academy of Sciences)

zhao-2025-09-15-HQL.pdf

zhao-2025-09-15-HQL.pptx

7 Recent spectroscopy results from LHCb experiment

Speaker: Zan Ren (UCAS)

Recent_spectroscopy_results_from_LHCb_experiment_final.pdf

8 Recent spectroscopy results from BESIII experiment

Speaker: Yateng Zhang (Zhengzhou University)

zhangythadron.pdf

9 Light and Strange Meson Spectroscopy: New Results on Exotic and High-Mass Mesons from the COMPASS Experiment

Speaker: Stephan Paul (Technical University of Munich)

HQL2025-Beijing_Paul.2.1.3 shown.pdf

12:35 Lunch

Neutrino Physics

Convener: Xuefeng Ding (Institute of High Energy Physics, Chinese Academy of Sciences)

10 Neutrino Masses and Mixing: Current Status and Open Questions

Speaker: Yufeng Li (IHEP, Beijing)

Neutrino-HQL-Beijing-202509.pdf

11 Status of the Hyper-Kamiokande experiment

Speaker: Jan Kisiel (University of Silesia in Katowice, Poland)

kisiel_Hyper-K_HQL2025_mduwt.pdf

12 The DUNE Experiment: Status and Outlook

Speakers: Jianming Bian (University of California, Irvine) , Jianming Bian (University of California, Irvine)

DUNE_HQL2025_2025_09_15.pdf

13 Neutrinos in the Multi-Messenger Era

Speaker: Piera Sapienza (INFN-LNS, Italy)

PIERASAPIENZA HQL 2025_final_xhwno.pdf

PIERASAPIENZA HQL 2025_ncjqn.pdf

16:10 Coffee break

Precision Lepton Measurements

Convener: Stephan Paul (Technical University of Munich)

14 LFV/LFU theory

Speaker: Marco Ardu

HQL2025_MArdu.pdf

15 Muon LFV/LFU measurements at JPARC, PSI, FNAL

Speaker: Yusuke Uchiyama

HQL2025.pptx

16 Tau LFV/LFU measurements

Speaker: Fabian Becherer

fabian_becherer_HQL2025.pdf

Tuesday, 16 September

Top Quark Physics

Convener: Hongbo LIAO (Institute of High Energy Physics)

17 Multi-top production calculation overview

Speaker: Qing-Hong Cao (Peking University)

Multi-top quark.pdf

18 Top quark properties measurements and searches for BSM signatures

Speaker: Huaqiao ZHANG (IHEP)

TopPropAndBSMSig_HuaqiaoZhang_HQL2025-V1.pdf

19 Top cross section and mass measurements

Speaker: Haifeng Li (Shandong University)

Top-XS-mass-v4.pdf

10:30 Coffee break

CP Violation

Convener: Wenbin QIAN (University of Chinese Academy of Sciences)

20 CP violation in b-baryon two body decays

Speaker: Jia-Jie Han

han-2025-HQL.pdf

21 TDCPV in B0 and Bs systems (results from LHCb, Belle II)

Speaker: Stefano Lacaprara

HQL2025_Lacaprara_20250916.pdf

22 Time-dependent results from ATLAS & CMS (including lifetimes and Bs->J/psi phi)

Speaker: Xin Chen (Tsinghua University)

talk_time_results_v3.pdf

23 CPV in charmless B meson decays (results from LHCb, Belle II)

Speaker: Mikihiko Nakao (KEK)

hql-charmless-nakao-v3.pdf

12:25 Lunch

Public forum

Convener: Guy Wilkinson (University of Oxford)

24 Public forum

Speaker: Guy Wilkinson (University of Oxford)

beijing_peking_flavour_sept25.pdf

15:00 Break

CKM Matrix

Convener: Biljana Mitreska

25 Recent results from LHCb on charged current decays of b-hadrons

Speaker: Jie Wu

Recent_results_from_LHCb_on_charged_current_decays_of_b_hadrons_JieWu_v2r5_nchys.pdf

26 New measurements of |Vcb| and |Vub| at Belle and Belle II

Speaker: Anja Novosel (Jozef Stefan Institute)

2025_09_HQL_an_fin.pdf

27 Experimental status of |Vcs| and |Vcd| at BES III

Speaker: Chao Chen (SUDA)

CKM_BESIII_20250916.pdf

Poster Session

28 Interferences in the quark sector of the general 2HDM from flavour physics

The general 2HDM allows for off-diagonal flavour violating couplings in the quark sector which are strongly constrained by experiments in traditional 2HDMs. We study how the allowed parameter space of the general 2HDM changes once interactions between 1-3 and 2-3 quark generations are included, generating new interference terms in the one loop diagrams relevant for meson mixing constraints and radiative decays. We show that this interference effect plays a crucial role in simultaneously fitting those constraints and the so-called charged current flavour anomalies. These couplings can be probed and further constrained by current and future measurements by the ATLAS detector via multi-top decay searches with multi-lepton and b-tagged jets.

Speaker: Cristian Sierra (上海交通大学)

HQL-Poster.pdf

HQL_slides_Cristian.pdf

29 First observation of the charmless baryonic decay $B^+\to\bar{\Lambda}p\bar{p}p$

Search for the charmless baryonic decay $B^+\to\bar{\Lambda}p\bar{p}p$ is performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 5.4$\text{fb}^{-1}$. The branching fraction is measured to be $\mathcal{B}(B^+\to\bar{\Lambda}p\bar{p}p) = (2.08 \pm 0.34 \pm 0.10 \pm 0.26) \times 10^{-7}$, where the first uncertainty is statistical, the second is systematic, and the third arises from the normalization channel. The $CP$ asymmetry is measured to be $\mathcal{A}_{CP}=(5.4\pm 15.6\pm 2.4)\%$, where the uncertainties are statistical and systematic. The background-subtracted invariant mass distributions of baryon-antibaryon pairs exhibit pronounced enhancements at both kinematic thresholds.

Speaker: Ying’ao Tang (Wuhan University)

LPPP_4minutes_talk_to_introduce_poster.pdf

LPPP_HQL_2025_poster.pdf

30 The measurement of H->cc/ss at the Circular Electron-Positron Collider

The measurement of Higgs decays to charm or strange quarks is crucial for probing the Higgs couplings to second-generation fermions. The electron-positron collider offers a clean collision environment with minimal QCD backgrounds, providing an excellent opportunity to study these couplings. By leveraging advanced deep learning techniques, the precision of the signal strength measurements for H → cc and H → ss can be improved by a factor of two to three compared to traditional cut-based methods at the Circular Electron-Positron Collider (CEPC).

Speaker: Yongfeng Zhu

HQL_zyf_zojsk.pdf

JOI_Poster_ocuxd.pdf

31 Novel $|V_{cb}|$ extraction via Lorentz-boosted bc-tagging at the LHC

We present a novel method for measuring $|V_{cb}|$ at general-purpose experiments at the LHC using an advanced boosted-jet tagger to identify "bc signatures". When combined with the conventional small-radius jet approach, this method achieves a ~30% improvement in $|V_{cb}|$ precision under HL-LHC projections, providing valuable insights into the $V_{cb}$ puzzle. By leveraging Lorentz-boosted topology, it substantially suppresses backgrounds and effectively reduces uncertainties in flavor tagging efficiencies through an in-situ calibration technique, critical for enhancing measurement precision.
This poster is based on the work of 2503.00118.

Speaker: Congqiao Li (Peking University)

arXiv:2503.00118

Poster_HQL2025_Vcb_CL.pdf

Slides_HQL2025_Vcb_CL.pdf

32 Study of the proton's internal structure via the photo-production process of vector mesons

Speaker: zeng fancong (Institute of High Energy Physics)

曾凡聪-粒子物理会议_海报.pdf

33 Evidence for H → μμ with CMS Run II Data and Projected Sensitivity at the HL-LHC

Evidence for Higgs boson decay to a pair of muons is presented, using proton-proton collision data at √s = 13 TeV, corresponding to an integrated luminosity of 137fb−1, recorded by the CMS experiment at the CERN LHC. This result
combines searches in four exclusive categories targeting the production of the Higgs boson via gluon fusion, via vector boson fusion, in association with a vector boson, and in association with a top quark-antiquark pair. An excess is observed with a significance of 3.0 standard deviations, where the expected significance is 2.5 for the Standard Model Higgs boson with a mass of 125.38 GeV. Extrapolations of the Run-2 H → μμ analyses from ATLAS and CMS to HL-LHC conditions predict a significant improvement in measurement precision.

Speaker: Qianying GUO

HQL2025_Poster_Qianying_v2.pdf

HQL2025_Qianying.pdf

34 Form factors in semileptonic decay $D_s\to\phi\ell\nu$ from lattice QCD

Semi-leptonic decays offer an ideal place to deeply understand hadronic transitions in the nonperturbative region of QCD and explore the weak and strong interactions in the charm sector. Combining with experimental data, the CKM matrix element can be extracted, and it helps to test unitarity of CKM matrix and searching for new physics beyond SM. In this talk, the full lattice QCD calculations of $D_s\to\phi\ell\nu$ decay form factors will be presented using CLQCD ensembles.

Speaker: Gaofeng Fan (Nanjing University)

Poster_HQL2025_Gaofeng.pdf

Talk_HQL2025_Gaofeng.pdf

35 Decay Selector: A web-based tool for Amplitude exploration

We present an web-based platform for Amplitude Analysis, designed to facilitate the exploration of multi-body decays. In such analyses, the large number of possible decay chains often presents a significant challenge in constructing amplitudes.
Our tool offers a user-friendly graphical interface (GUI) that enables efficient sorting, filtering, filling, and validation of decay chains. Previously saved setups can be easily uploaded and resumed, allowing for a seamless continuation of work. Integration with the Particle Data Group (PDG) API enables quick inclusion of known resonances. Configurations can be saved and exported both as JSON files and as executable code within a custom framework using the helicity formalism to parameterize the angular structure of the amplitudes. We aim to collaborate with other developers to support multiple frameworks through dedicated parsers, thereby broadening the tool’s applicability to the wider amplitude analysis community.

Speaker: Kai Habermann (University of Bonn)

DecaySelectorFlashTalk.pdf

DecaySelector_Poster-Final.pdf

36 Precision calculation of charm baryon decay constants in lattice QCD

We present the first calculation of charmed baryon decay constants using 2+1 flavor gauge ensembles with lattice spacings ranging from 0.05 to 0.1 fm and pion masses between 136 and 310 MeV. Under SU(3) flavor symmetry, we construct the charmed baryon interpolating operators and compute the corresponding hadronic matrix elements to extract the bare decay constants for each ensemble. The non-perturbative renormalization is performed using the symmetric momentum-subtraction (SMOM) scheme. After performing systematic chiral and continuum extrapolations, we obtain the decay constants with 4-11% precision.

Speaker: Leiyi Li (上海交通大学)

Calculation of Decay Constants of Charmed Baryons_wvwbd.pdf

poster Lileiyi_20250916162201.pdf

37 Full angular analysis of the B^0→K^* (892)^0 μ^+ μ^- decay in proton-proton collisions at CMS

A complete set of optimized CP-averaged angular observables in the rare flavor-changing neutral-current decay $B^0 \rightarrow K^*(892)^0 \mu^+ \mu^-$, with $K^*(892)^0 \rightarrow K^+ \pi^-$, is measured using the full Run 2 dataset of proton-proton collisions at $\sqrt{s} = 13 \ \rm{TeV}$ collected by the CMS detector, corresponding to an integrated luminosity of 140 $\rm{fb}^{-1}$. The analysis is performed in six bins of the dimuon invariant mass squared ($q^2$) over the range 1.1<$q^2$<16 $\rm{GeV}^2$, excluding the charmonium resonance regions. Angular parameters are obtained through unbinned maximum-likelihood fits to the reconstructed $B^0$ candidate mass and three decay angles, with detailed efficiency modeling and background parameterization. The measured observables achieve among the highest precision to date for this decay mode, enabling stringent tests of Standard Model predictions. Comparisons with multiple theoretical calculations reveal local tensions in specific observables, notably $P'_5$ and $P_2$, consistent with anomalies reported by other experiments. These results provide a valuable contribution to the understanding of the $b \rightarrow s l^+l^-$ processes.

Speaker: Xuelong Qin (Peking University; Laser Fusion Research Center)

HQL_Kmumu_Poster_v0.pptx

HQL_Kmumu_slides_v0.pdf

38 Probing Charm Production in Cold Nuclear Matter with the CBM Proton Beam Program

The Compressed Baryonic Matter (CBM) experiment at FAIR, with its unprecedented rate capabilities and precision vertexing, offers a unique opportunity to advance charm physics through its dedicated proton beam program. A central objective of this program is to investigate the production and propagation of charm hadrons in cold nuclear matter. Such studies will provide indispensable baseline measurements for heavy-ion collisions and deliver novel insights into the microscopic dynamics of the strong interaction.

The combination of excellent tracking, robust particle identification, and ultra-fast readout in CBM will facilitate high-precision measurements of charm production cross sections, nuclear modification factors, and flow observables at interaction rates beyond current experimental reach. These measurements are crucial for disentangling cold nuclear matter effects from those of the hot and dense medium created in heavy-ion collisions. Ultimately, the CBM proton program will refine our understanding of parton energy loss, hadronization mechanisms, and the manifestation of the strong force across the transition from hadronic to partonic degrees of freedom.

Exploiting a high-intensity proton beam on a variety of fixed targets, CBM will access rare charm probes—including open charm mesons (D⁰, D±), charm baryons (Λc), and hidden charm states (J/ψ, ψ′). The Micro Vertex Detector (MVD), with a decay-vertex resolution of about 50 μm, enables precise reconstruction of open charm decays. In this work, we demonstrate the performance of open charm meson and baryon reconstruction using the KFParticle Finder package, and discuss the challenges of primary vertex determination in events with multiple high-momentum charm particles.

Speaker: Prof. Ivan Kisel (Uni-Frankfurt, FIAS)

I. Kisel and I. Vassilev, Flash Talk HQL2025, Probing Charm Production in Cold Nuclear Matter with the CBM Proton Beam Program.pdf

I. Kisel and I. Vassilev, Poster HQL2025, Probing Charm Production in Cold Nuclear Matter with the CBM Proton Beam Program.pdf

39 Observation of a family of all-charm tetraquarks at CMS

Three enigmatic structures, X(6600), X(6900), and X(7100), have emerged from the J/ψJ/ψ (J/ψ → μ+μ−) spectrum as candidate all-charm tetraquarks, a rare and exotic form of matter. Using 315 fb^{−1} of proton-proton collisions data recorded by the CMS detector, yielding 3.6 times more J/ψJ/ψ pairs than previous studies, one can achieve a sharper view of these states, with significantly improved precision. All three structures and the interference among them are observed with a statistical significance above five standard deviations, suggesting common JPC quantum numbers.

Speaker: Yilin Zhou (Fudan University)

20250916HQL2025_Poster.pdf

40 Observation of X(6900) and evidence of X(7100) in the $J/\psi\psi(2S) \rightarrow \mu^{+} \mu^{-} \mu^{+} \mu^{-}$ mass spectrum

In the study of the $J/\psi$$J/\psi$ invariant mass spectrum, the CMS collaboration has observed three distinct structural features, labeled as X(6600), X(6900), and X(7100). In-depth analysis of the experimental data suggests that a theoretical model incorporating the quantum interference effects of these three resonance states best describes the observed mass spectrum distribution characteristics. This discovery implies that these three states share the same spin-parity quantum numbers ($J^{PC}$), providing crucial clues for understanding the nature of these exotic states.
As an extension in the $ J/\psi\psi(2S)$ decay channel, the search is performed for structures near threshold in the $J/\psi\psi(2S) \rightarrow \mu^{+} \mu^{-} \mu^{+} \mu^{-}$ channel using a sample of proton-proton collisions at $\sqrt{s} = 13.0~\mathrm{TeV}$ and $13.6~\mathrm{TeV}$ recorded by the CMS detector at the CERN LHC. The data correspond to an integrated luminosity of about $315~\mathrm{fb}^{-1}$. A threshold structure is observed near $6900~\mathrm{MeV}$ with a significance in excess of five standard deviations ($>$5$\sigma$), and there is also evidence (4.3$\sigma$) for a second peak, in a model where the structures mutually interfere. The mass and width of the two peaks are measured to be $~6876^{~+46}_{~-29} \pm 110$, $~253^{~+290}_{~-100}\pm 120~\mathrm{MeV}$ and $~7169^{~+26~+74}_{~-52~-70}$, $~154^{~+110~+140}_{~-82~-160}~\mathrm{MeV}$, which are consistent to within one standard deviation of the X(6900) and X(7100) structures previously observed in the $J/\psi$$J/\psi$ spectrum.

Speaker: Liangliang Chen

CLL_HQL2025_yilinz.pdf

CLL_HQL2025_yilinz.pptx

psi2sjpsi_llchen.pdf

41 Determination of the spin and parity of all-charm tetraquarks

The traditional quark model accounts for the existence of baryons, such as protons and neutrons, which consist of three quarks, as well as mesons, composed of a quark-antiquark pair. Only recently has substantial evidence started to accumulate for exotic states composed of four or five quarks and antiquarks. The exact nature of their internal structure remains uncertain. This paper reports the first measurement of quantum numbers of the recently discovered family of three all-charm tetraquarks, using data collected by the CMS experiment at the Large Hadron Collider from 2016 to 2018. The angular analysis techniques developed for the discovery and characterization of the Higgs boson have been applied to the new exotic states. The quantum numbers for parity P and charge conjugation C symmetries are found to be +1. The spin J of these exotic states is consistent with 2ℏ, while 0ℏ and 1ℏ are excluded at 95% and 99% confidence level, respectively. The JPC=2++ assignment implies particular configurations of constituent spins and orbital angular momenta, which constrain the possible internal structure of these tetraquarks.

Speaker: Xining Wang (Tsinghua University)

HOL_4mintalk_9.16pm_Xining_Wang_sgnlf.pdf

HQL_poster_9.16pm_Xining_Wang_lqriy.pdf

42 Positron Detection System of Muonium-to-Antimuonium Conversion Experiment

The Muonium-to-Antimuonium Conversion Experiment (MACE) aims to investigate charged lepton flavor violation (cLFV) through investigating spontaneous muonium-to-antimuonium conversion. This process is detected using a positron detection system (PDS), which consists of a lead-free microchannel plate (MCP) and a BGO electromagnetic calorimeter (ECal). In this study, we conducted preliminary prototype experiments to evaluate the performance of the PDS. Using photomultiplier tubes (PMTs) coupled with BGO scintillation crystals, we measured the detector's time resolution, achieving a value of approximately 2.6 ns. Additionally, utilizing a positron beam at the Institute of High Energy Physics (IHEP), we determined the detection efficiency of the lead-free MCP for positrons in the energy range of 300 eV to 1200 eV, obtaining an efficiency about 30%. These results demonstrate the feasibility of the PDS for the MACE and provide critical insights into its operational performance.

Speaker: Huaxing Peng

phx_mace_poster.pdf

phx_mace_slide.pdf

43 (poster-only) 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 $e^+e^- \to \Lambda_c^{+}\bar{\Lambda}_c^-$, based on $6.4~\text{fb}^{-1}$ 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 $\Lambda_c^+ \to pK_S^0$, $\Lambda\pi^+$, $\Sigma^0\pi^+$, $\Sigma^+\pi^0$ 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: Hao Sun (UCAS)

1_HQL25POSTER_oxkxe.pdf

44 (poster-only) Helicity amplitude analysis of chi_cJ -> phi phi

Charmonium state decays provide critical insights into Quantum Chromodynamics (QCD) dynamics. Early theoretical frameworks interpreted two-meson charmonium decays as perturbative QCD (pQCD) processes following helicity selection rules (HSR). BESIII observations of comparable chic1→phi + phi and chic0/chic2→phi + phi branching fractions demonstrate explicit HSR violations, compelling incorporation of non-perturbative QCD mechanisms. Three competing frameworks, pQCD with phi meson polarisation, 3P0 quark creation models, and DD-loop model, predict distinct helicity amplitude ratios for chicj→phi phi decays. Validation is performed through dedicated helicity amplitude analysis of 448.1 million psi(3686) events. Measured helicity amplitude ratios exhibit discrepancies from all theoretical predictions, challenging current chicj decay interpretations. These results necessitate the new non-perturbative QCD mechanisms and provide more constraints for further developing the models.

Speaker: Boan Shi (UCAS)

2025_HQL_poster.pdf

45 (poster-only) Study of $\chi_{c}$ production in pPb collisions at $\sqrt{s_{NN}}=8.16 TeV$ energy with the CMS experiment

The modification of quarkonium state production in the deconfined QCD medium in nuclear collisions does not solely originate from the medium dissociation but rather is a collection of effects from initial to final states. Excited charmonium production in pPb collision can be thought of as a controlled environment to understand these effects. In particular, the production of the $chi_c$ mesons, as p-wave quarkonium states, can provide more information about the feed-down and binding energy dependence of the charmonia in the nuclear collisions, as their masses lie in between the ground state and the $\psi(2S)$. In this talk, we present analysis results of the production of $chi_c$ in pPb collisions at center-of-mass energy per nucleon pair of $\sqrt{s_{NN}}=8.16 TeV$. The data are collected by the CMS detector and correspond to an integrated luminosity of 175 $nb^{-1}$. The analysis measures the relative production of $\chi_{c1,2}$ with respect to $J/\psi$ as a function of particle transverse momentum and rapidity, and event activity. The results are compared with other experiment measurements at the LHC with different rapidity ranges and proton-proton collision data and model calculation to further extend our understanding of $\chi_{c}$ state production in nuclear collisions. Given that the relative cross sections are consistent with the proton-proton results at similar collision energies, the findings rule out a strong additional suppression of the $\chi_{c}$ states relative to the $J/\psi states in pPb collisions.

Speaker: 曈光 成 (Beihang University)

poster_HQL2025.pdf

46 (poster-only) Helicity amplitude and branching fraction measurement of $\chi_{cJ} \to \Lambda\bar{\Lambda}$

We present a comprehensive partial wave analysis of $\psi(3686) \to \gamma\chi_{cJ} \to \gamma\Lambda\bar{\Lambda}$ decays ($J=0,1,2$) using $2712.4 \pm 14.3$ million $\psi(3686)$ events collected by the BESIII experiment. This analysis provides the first determination of the helicity amplitude ratio for $\chi_{c2} \to \Lambda\bar{\Lambda}$ decay, yielding $R_{\chi_{c2}} = 0.575 \pm 0.048 \pm 0.018$ with relative phase angle $\Delta\Phi_{\chi_{c2}} = 0.37 \pm 0.15 \pm 0.05$~rad. The angular distribution parameters are measured as $\alpha_{\chi_{c2}} = -0.211 \pm 0.100 \pm 0.050$ and $\beta_{\chi_{c2}} = -0.039 \pm 0.089 \pm 0.033$, based on the distribution $\frac{dN}{d\cos\theta} = 1 + \alpha_{\chi_{c2}} \cos^2\theta + \beta_{\chi_{c2}} \cos^4\theta$. In our partial wave analysis, we have incorporated detector resolution effects in the invariant mass spectrum of $\chi_{cJ}$ states, and extracted the width of $\chi_{c0}$ as $12.31 \pm 0.26 \pm 0.12$~MeV. Additionally, we report precise branching fraction measurements: $\mathcal{B}(\chi_{c0} \to \Lambda\bar{\Lambda}) = (3.662 \pm 0.048 \pm 0.111) \times 10^{-4}$, $\mathcal{B}(\chi_{c1} \to \Lambda\bar{\Lambda}) = (1.182 \pm 0.026 \pm 0.042) \times 10^{-4}$, and $\mathcal{B}(\chi_{c2} \to \Lambda\bar{\Lambda}) = (1.704 \pm 0.035 \pm 0.057) \times 10^{-4}$, where uncertainties are statistical and systematic, respectively. These results provide crucial insights into the helicity selection rule violations in P-wave charmonium states decays.

Speaker: Ruoping Zhao (University of Chinese Academy of Sciences)

chicj_poster_v4.pdf

Wednesday, 17 September

Kaon physics

Convener: Francesco Brizioli (INFN Perugia (IT))

47 Standard Model predictions for kaon decays

Speaker: Xu Feng (Peking University)

SM_kaon_decays_Short_version.pptx

48 Status and future prospects for rare kaon decay measurements at NA62

Speaker: Renato Fiorenza (INFN Napoli and CERN)

Fiorenza_HQL2025.pdf

49 Status and future prospects for rare kaon decay measurements at KOTO(-II)

Speaker: Ryota Shiraishi (Osaka University)

2025_0917_koto.pdf

50 Status and future prospects for rare kaon decay measurements at LHCb and other LHC experiments

Speaker: Luis Miguel Garcia Martin (EPFL)

KaonsAtLHCb_HQL2025.pdf

10:30 Coffee break

Kaon physics

Convener: Francesco Brizioli (INFN Perugia (IT))

51 Long-distance contributions to Kaon decays on the lattice

Speaker: En-Hung Chao (Columbia University)

hql2025-rarek.pdf

CP Violation

Convener: Wenbin QIAN (University of Chinese Academy of Sciences)

52 Theory of charm lifetimes, mixing and CP violation

Speaker: Chia-Wei Liu

Chia-Wei_Liu_Sep_17.pdf

53 CPV in charm (results from LHCb, Belle II, BESIII, CMS)

Speaker: Xinchen Dai

CPV_in_Charm_HQL2025_Beijing.pdf

54 Quantum-correlation of neutral charmed mesons at BESIII

Speaker: Wenhan Shen (University of Chinese Academy of Sciences)

QC.pdf

55 Gamma including BESIII inputs (results from LHCb, Belle II, BESIII)

Speaker: Aidan Richard Wiederhold (University of Manchester)

AidanWiederhold_HQL_final.pdf

Thursday, 18 September

Neutrino Physics

Convener: Jan Kisiel (University of Silesia in Katowice, Poland)

56 Long-Baseline Neutrino Experiments: A Journey from Discovery to Precision and Beyond

Speaker: Lucio Ludovici (INFN Roma)

HQL-LongBaseline.pdf

57 Experimental progress in neutrinoless double beta decay with a focus on LEGEND

Speaker: Pin-Jung Chiu (Department of Physics National Taiwan University)

2025-09-18-Chiu-HQL2025-Beijing.pdf

58 Neutrinos and BSM Searches

Speaker: Michele Lucente (UNiversity of Bologna, Italy)

Neutrinos_BSM.pdf

59 JUNO status and prospects

Speaker: Jie ZHAO (高能所)

HQL2025_JUNO_zj.pdf

10:40 Coffee break

CKM Matrix

Convener: Biljana Mitreska

60 Theory overview on semileptonic decays

Speaker: Cai-Dian Lu (高能所)

Reviewofsemi-lepton.pdf

61 Inclusive and exclusive semileptonic decays of heavy-mesons on lattice

Speaker: Zhi Hu

Inclusive and exclusive semileptonic decays of heavy-mesons on lattice-HQL-Zhi Hu_xrgmp.pdf

62 Recent Belle II results on tests of lepton flavour universality in semileptonic B-meson decays

Speaker: Karol Adamczyk (Institute of Nuclear Physics Polish Academy of Sciences)

HQL_20250918_v3.pdf

12:15 Lunch

Spectroscopy

Convener: Zehua Xu (CERN)

63 Physics of multiquark states

Speaker: Feng-Kun Guo (ITP, CAS)

Multiquarks_HQL_FKGuo.pdf

64 Recent spectroscopy results from Belle II experiment

Speaker: Junhao YIN (南开大学)

Belle2Spectroscopy-JHYin-0918.pdf

65 Recent spectroscopy results from ATLAS and CMS experiments

Speaker: Zhen Hu (Tsinghua University)

20250918-HQL-ZhenHu.pdf

66 Recent results on heavy quarks and leptons from Alice experiment

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

HQL25_xbai_v5.pdf

16:05 Coffee break

Spectroscopy

Convener: Zehua Xu (CERN)

67 Prospect of hadron spectroscopy at future experiments

Speaker: Beijiang LIU (高能所)

BJLiu_HQL2025.pdf

Rare decays

Convener: Mikihiko Nakao (KEK)

68 Rare charm decays - theory overview

Speaker: Yuji Shi (Shanghai Jiaotong University)

Shi Yuji- Rare charm decay theory overview_ywoip.pptx

69 Rare charm/charmonium decays from BESIII

Speaker: Guorong Che (Nankai university)

rare_charm_decay_Guorong.pdf

70 The semi-leptonic decays of charmed hadrons at BESIII

Speaker: Yangu Li (University of Chinese Academy of Sciences)

Charm_SL_BESIII_250918.pdf

Friday, 19 September

Rare decays

Convener: Liang Sun (Wuhan University)

71 Rare b decays - theory overview

Speaker: Yue-Long Shen (Ocean University of China)

Rare-b-decays.pdf

72 Rare heavy flavor decays from ATLAS / CMS

Speaker: Dayong Wang (Peking University)

20250919_HQL2025_PKU.pdf

73 Rare b decay from BelleII

Speaker: Caspar Schmitt (LMU Munich (Germany))

HQL25Final.pdf

74 Rare decays at LHCb

Speaker: Thomas Long

ThomasLong_HQL_RD_final.pdf

10:30 Coffee break

Precision Lepton Measurements

Convener: Lorenzo Calibbi (Nankai University)

75 Non-tau LFV/LFU measurements at Belle and Belle II

Speaker: Sourav Patra (University of Cincinnati)

sourav_patra_hql_2025.pdf

76 Measurements of magnetic and electric dipole moments of hadrons

Speaker: Nicola Neri (INFN Pisa)

Neri_HQL25_Beijing.pdf

77 Measurements of lepton flavour universality at LHC

Speaker: Lucas Martel

HQL_talk_Martel_gfavw.pdf

12:15 Lunch

New experiments

Convener: Haibo LI (高能所)

78 Flavour prospects at FCC-ee

Speaker: Guy Wilkinson (University of Oxford)

HQL_FCC_flavour.pdf

79 Flavour prospects at CEPC

Speaker: Lingfeng Li (HKUST)

Flavor_White_Paper_HQL2025.pdf

80 The Super Tau-Charm Facility

Speaker: Cong Geng (Sun Yat-Sen (Zhongshan) University)

STCF-HQL2025-GC - 2.pdf

81 FASERν2, FLArE and other future nu exp. at collider

Speaker: Wenjie Wu (CAS)

20250919@HQL2025-FPFOverview.pdf

Poster Award + Closing Remarks

Convener: Liupan An (Peking University)