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The 3rd Edition of the Spicy Gluons (胶麻) Workshop for Young Scientists on the Quark-Gluon Matter in Extreme Conditions
October 17–20, 2026
(Oct 17: registration only. Scientific program starts from Oct 18)
Location: 武汉东湖濮锦酒店 (Pujin Hotel, Wuhan)
The workshop is dedicated to young scientists, only students and young postdoc/faculty within 5 years of Ph.D. are considered.
本研讨会专为在读学生及博士毕业5年内的青年科学家开设。
We look forward to seeing you in Wuhan for stimulating science and spicy discussions!
We report the first measurements of two-particle transverse-momentum correlations for midrapidity charged particles in fixed-target Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=3.0$--$7.7$ GeV using data collected by STAR during the Beam Energy Scan Phase II program [1]. Combined with previous BES-I measurements at $\sqrt{s_{\mathrm{NN}}}=7.7$--$200$ GeV [2], the relative dynamical correlator approximately follows the $1/\sqrt{N_{\mathrm{part}}}$ scaling expected from independent particle-emitting sources at most energies. The scaling breaks down at the lowest collision energy, while additional deviations emerge in central collisions. For 0--5% central collisions, the combined data exhibit a non-monotonic beam-energy dependence with a significance of approximately $5\sigma$ relative to a monotonic baseline. In comparison, the mid-central data and AMPT calculations yield deviations of only approximately $2\sigma$ and $1.4\sigma$, respectively. Possible connections to temperature fluctuations and QCD critical dynamics are discussed using recent $2+1$-flavor LEFT-fRG and PNJL model calculations [3, 4]. These observations provide valuable input to probe critical fluctuations in the vicinity of the QCD critical point and new constraints on the equation of state at high baryon density.
[1] STAR Collaboration, "Non-Monotonicity of Transverse Momentum Correlations in Au+Au Collisions at RHIC," arXiv:2604.06434 [nucl-ex] (2026), accepted for publication in Physical Review Letters.
[2] STAR Collaboration, "Collision Energy Dependence of $p_{\mathrm{T}}$ Correlations in Au+Au Collisions at RHIC," Phys. Rev. C 99, 044918 (2019).
[3] J. Chen, W.-j. Fu, S. Yin, and C. Zhang, "High-Order Fluctuations of Temperature in Hot QCD Matter," arXiv:2504.06886 [hep-ph] (2025), accepted for publication in Physical Review D.
[4] H. Liu, P. Wu, H.-M. Liu, and P.-C. Chu, "Temperature Fluctuations in a Realistic Polyakov-Loop Extended Nambu--Jona-Lasinio Model along the Freeze-Out Line," arXiv:2607.19275 [nucl-th] (2026).
We present recent STAR measurements of the newly proposed radial flow fluctuation coefficient, $v_{0}(p_{T})$, for identified hadrons in heavy-ion collisions at RHIC. As a direct probe of the isotropic component of collective expansion, $v_{0}(p_{T})$ is uniquely sensitive to both the strength and event-by-event fluctuations of radial flow, offering new constraints on the initial-state geometry and transport properties of the created medium. The analysis encompasses both top RHIC energies and the full Beam Energy Scan (BES) program, covering $\sqrt{s_{NN}} = 11.5$ - $200$ GeV.
Using the STAR detector's large-acceptance dataset, we report the first systematic measurements of $v_{0}(p_{T})$ for a comprehensive set of identified hadrons, including $\pi^{\pm}$, $K^{\pm}$, $p$, $\bar{p}$, $\Lambda$, $\bar{\Lambda}$, $K^{0}_{S}$, $\Xi^{-}$, $\bar{\Xi}^{+}$, and $\phi$ mesons. The mass ordering of $v_{0}(p_{T})$ is investigated, and its Number-of-Constituent-Quark (NCQ) scaling is tested to examine whether radial flow, similar to elliptic flow, originates from partonic degrees of freedom. The energy dependence of $v_{0}(p_{T})$ is further scrutinized to map the evolution of collective dynamics across the QCD phase transition region. Comparisons with hydrodynamic and transport models provide stringent tests of theoretical descriptions and shed new light on the development of radial flow and its fluctuations as a function of collision energy.
磁化 QCD 物质中的守恒荷涨落与关联，以及温度涨落，在手征恢复相变和禁闭解除相变过程中被广泛研究，包括交叉区域以及临界终点（ CEP）附近区域。相关计算在三味（Polyakov 扩展的）Nambu–Jona-Lasinio 模型框架下进行。对于有限温度下的交叉过程，我们重点研究这些物理量对外部磁场的依赖关系，并发现重子数与其他守恒荷之间的关联对外部磁场最为敏感。对于有限温度和有限密度下的 CEP 区域，我们系统地计算了最高达十阶的涨落与关联，以理解其临界性质。
In this work, we construct a theoretical framework for relativistic second-order magnetohydrodynamics based on entropy current analysis. The formalism consistently incorporates the relaxation dynamics of dissipative fluxes, ensuring the hyperbolic nature of the evolution equations. Utilizing linear mode analysis, we investigate the constraints imposed by causality and stability on this anisotropic system. By linearizing the theory around a homogeneous equilibrium state, we demonstrate that the excitation spectrum decomposes into magnetosonic, Alfv\'en, and charge-diffusion sectors. For each sector, we derive asymptotic dispersion relations in both the long-wavelength (small-$k$) and short-wavelength (large-$k$) regimes, validating them against exact numerical roots. Our numerical analysis confirms the accuracy of these asymptotic solutions and uncovers a nontrivial angular dependence, especially near special propagation directions where the ordinary momentum expansion becomes less reliable. By evaluating the large-$k$ behavior of the propagating branches alongside the damping properties of non-hydrodynamic modes, we delineate the corresponding causality constraints. We find that the admissible causal domain is governed by the interplay between anisotropic transport coefficients and relaxation times, with the resulting bounds being intrinsically mode-dependent. These findings provide a systematic theoretical foundation for developing stable and causal relativistic magnetohydrodynamics beyond the first-order approximation.
Energy and momentum deposited by energetic partons in the quark-gluon plasma (QGP) generate a Mach-cone-like jet-induced medium response consisting of a propagating wake front and a diffusion wake. In realistic heavy-ion collisions, this response evolves in a nonuniform and expanding medium and is therefore distorted by the density gradient and hydrodynamic flow. Using the coupled Linear Boltzmann Transport and hydrodynamic (CoLBT-hydro) model, we show that the elliptic geometry and elliptic flow in non-central collisions lead to an azimuthally dependent broadening of the jet wake. We propose differences between in-plane and out-of-plane jet-hadron correlations, including their azimuthal dependence and rapidity asymmetries, as observables of the broadening of the wake front and the deepening of the diffusion wake. Their sensitivity to the shear viscosity provides a possible means of constraining the transport properties of the QGP.
To enable more extensive studies of such medium responses, we further train a Flow Matching generative model using CoLBT-hydro $\gamma$-jet events in $0$--$10\%$ Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~\mathrm{TeV}$. Conditioned only on the initial spatial and momentum information of the photon and jets, the model generates the final-state soft-hadron spectrum$\frac{\mathrm{d}^{3}N} {\mathrm{d}p_T\,\mathrm{d}\eta\,\mathrm{d}\phi}$. It reproduces the statistical properties of both the wake front and the diffusion wake while achieving an acceleration of approximately six orders of magnitude relative to full CoLBT-hydro simulations. These results provide both experimentally accessible observables and an efficient generative framework for studying jet-induced medium response in heavy-ion collisions.
One method used to infer the mass and radius of a neutron star is Pulse Profile Modelling (PPM). PPM connects X-ray emission from localized regions on the neutron star's surface to a modulated signal seen in X-ray detectors (such as NICER). The analysis requires relativistic raytracing， which creates a computational bottle-neck that leads to two issues: the analysis of data is very slow， and that the analysis is restricted to very simple spot models (a few circles).In this talk， I will introduce a new code that implements the raytracing algorithm run on GPU， instead of the more traditional CPU. This introduces a significant speed-up of the computations required. I will show that this speed-up does not compromise the accuracy of the modelling. Our new code also allows for more complicated spot patterns， which could， in the future， be used to model physically-motivated spots that are connected to magnetic field geometries.
Strong first-order QCD phase transitions from hadronic to quark matter can produce disconnected hybrid-star branches, and the evolution and fate of stellar configurations close to the onset of the unstable branch triggered by the phase transition may depend on finite-temperature and composition effects in the equation of state (EOS). To investigate these aspects, we perform three-dimensional (3D) general relativistic hydrodynamic (GRHD) simulations using the WhiskyTHC code, and adopt representative hybrid-star EOSs with a Maxwell construction. We compare four thermodynamic treatments of the hybrid EOS: (i) a cold barotropic EOS implemented with constant thermal gamma-law pressures, (ii) a specific table imposed with fixed temperature, (iii) a specific table enforced with beta equilibrium conditions, and (iv) a full 3D table $P(\rho,T,Y_e)$. Under all four EOS treatments, configurations initialized on the stable hybrid branch remain on this branch throughout the evolution and retain their quark cores. For typical hybrid configurations on the unstable branch, our results indicate that only the full 3D table preserves a hot, low-Ye quark core over our simulation timescale, highlighting the significance of incorporating realistic microphysics in evaluating the dynamics and stability of hybrid stars.
We investigate the applicability of hydrodynamics in small collision systems by comparing viscous anisotropic hydrodynamics (VAH) with conventional viscous hydrodynamics (VH). In $\sqrt{s}=13$ TeV p+p collisions, VAH successfully describes $v_2\{2\}$, $v_3\{2\}$, and the negative $c_2\{4\}$, whereas VH requires evolution characterized by large shear Knudsen numbers. We further compare VAH and VH in $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV O+O and Ne+Ne collisions. Their predictions are generally similar, but differences emerge in $v_3\{2\}$ and $v_4\{2\}$ in peripheral collisions. These results help constrain the applicability of conventional hydrodynamics and quantify non-equilibrium effects across small collision systems.
We investigate spin hydrodynamic properties with an focus on entropy production for massive spin 1/2 particles. We consider particle collisions both with and without the influence of chiral anomalies such as the chiral magnetic or vortical effects, encoded by Berry curvature. This manifests as a spatial shift ($\Delta$). In doing so we first define and entropy that makes use of the matrix valued distribution function without the influence of a spatial shift. We show that the entropy production is positive definite. Then we extend the definition to include effects of the spatial effects in two ways. First, we absorb the average center of mass (COM) shift ($\bar \Delta$) into the definition of the distribution so that we can isolate the effect of the remaining relative shift $\Delta_{rel}$. we find that near thermodynamic equilibrium this relative entropy is also positive definite. Otherwise, the effect due to $\Delta_{rel}$ must be treated as a small correction to the shift free entropy production. Finally, we consider a form of entropy that includes both the COM and relative shifts. This entropy production is manifestly positive definite and naturally extends to the massless limit as seen in chiral kinetic theory.
Strong magnetic fields produced in relativistic heavy-ion collisions can modify conserved-charge fluctuations and their associated chemical potentials. The Ru and Zr isobars share the same mass number, $A=96$, but have different charge-to-baryon ratios, making Ru+Ru and Zr+Zr collisions a controlled setting for isolating isospin effects. In this talk, we will present first-principles, continuum-estimated $(2+1)$-flavor lattice-QCD results for isospin-driven splittings of conserved-charge chemical potentials near the QCD crossover, at both vanishing and nonzero external magnetic fields along the pseudocritical line $T_{\mathrm{pc}}(eB)$. Under strangeness neutrality and the charge-to-baryon constraint $r\equiv n_Q/n_B$, the difference in nuclear isospin composition is mapped onto the splitting ratios $\Delta\mu_Q/\Delta\mu_B$, $\Delta\mu_S/\Delta\mu_B$, and $\Delta\mu_S/\Delta\mu_Q$. At vanishing magnetic field, the lattice results yield $\Delta\mu_Q<0$ and $\Delta\mu_S>0$, with the electric-charge sector dominating, and the splitting ratios are similar in magnitude to recent Bayesian extractions from STAR isobar data. At nonzero magnetic fields, the splitting ratios themselves vary only moderately with $eB$. A clearer field signal emerges from the Ru-Zr difference in the normalized magnetic-field response: in lattice QCD, the relative response of $\mu_Q/\mu_B$ is substantially stronger in Ru+Ru than in Zr+Zr. We also present hadron resonance gas (HRG) results and experimentally motivated proxy observables with kinematic cuts to facilitate contact with experiment. These results provide first-principles benchmarks for the conserved-charge response to isospin and magnetic fields in isobar collisions.
This talk is based on our recent work: H.-T. Ding, J.-B. Gu, A. Kumar, and J. Ni, arXiv:2606.30164 [hep-lat] (2026).
Recent O+O and Ne+Ne collisions at the LHC provide a controlled laboratory to test the applicability of relativistic hydrodynamics and search for signatures of quark-gluon plasma formation in small systems. We study O+O and Ne+Ne collisions at $\sqrt{s_{\mathrm{NN}}}=5.36~\mathrm{TeV}$ using two complementary approaches.
First, we compare viscous anisotropic hydrodynamics (VAH) with conventional viscous hydrodynamics (VH). After calibrating both frameworks to selected flow observables, we systematically scan higher-order flow harmonics and nonlinear flow correlations. The two frameworks give similar predictions over a broad centrality range, while appreciable differences emerge for selected observables toward peripheral collisions. These results quantify nonequilibrium effects and constrain the range of validity of conventional hydrodynamics.
Second, within the Hydro-Coal-Frag framework, we combine hydrodynamics at low $p_T$, quark coalescence at intermediate $p_T$, and fragmentation at high $p_T$. The calculations provide a good description of the available ALICE data and exhibit approximate number-of-constituent-quark scaling at intermediate $p_T$. This scaling provides an important signature of partonic degrees of freedom and QGP droplet formation in O+O and Ne+Ne collisions.
It has recently been realized that in the ultra-central heavy-ion collisions, mean transverse momentum of hadrons contains the information of the fundamental thermodynamic properties of quark-gluon plasma (QGP). In particular, in nucleus-nucleus collisions, the linear correlation between the mean transverse momentum and the charged multiplicity is attributed to the QCD speed of sound, which promotes both theoretical and experimental investigations. However, in realistic collisions, these studies suffer from the contamination of fluctuations, especially the quantum fluctuations from the initial state, which bias the extracted value. Traditional analyses struggle to separate this fluctuating background from the genuine thermodynamic signal.
In this talk, we present a systematic subtraction scheme to resolve this issue. In a thermalized QGP, the quantum fluctuations $\delta$ are independent from the thermodynamic responce and vary randomly across events. According to the Central Limit Theorem, the distribution of $\delta$ should approach Gaussianity allowing us to extract the physical speed of sound statistically even in the presence of these fluctuations. Crucially, this approach can also serve as a direct probe of QGP thermalization. In a non-thermalized system, the distribution of $\delta$ deviates from Gaussianity and the extracted value of speed of sound is non-physical. The deviations from thermalization can be quantified by the standardized kurtosis $\kappa_4$ of $\delta$.
Validated by the event-by-event hydrodynamic simulations, the extracted speed of sound in our framework is successfully consistant with the predictions from lattice QCD, from large to small collision systems. To enhance statistical robustness, we also employ AI-powered diffusion model for data augmentation, which further strengthen the reliability of our results.
Event-by-event fluctuations of the mean transverse momentum of particles provide a direct probe of collective radial expansion of the system formed in high-energy collisions. We present the first measurement of transverse-momentum-dependent radial flow fluctuations, characterized by the observable $v_0(p_{\mathrm{T}})$, in small collision systems. The measurement is performed using CMS data from pp collisions at $\sqrt{s}=13~\mathrm{TeV}$, pPb collisions at $\sqrt{s_{\mathrm{NN}}}=8.16~\mathrm{TeV}$, and OO, NeNe and peripheral PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=5.36~\mathrm{TeV}$. The observable is measured from two-particle correlations with a pseudorapidity gap to suppress short-range nonflow contributions. The transverse-momentum dependence is investigated through the normalized quantity $v_0(p_{\mathrm{T}})/v_0$ as a function of $p_{\mathrm{T}}/\langle p_{\mathrm{T}}\rangle$, providing a systematic comparison across multiplicity and collision systems. The results are compared with hydrodynamic calculations based on TRENTO+MUSIC initial conditions, as well as predictions from the nonthermal event generators PYTHIA and HIJING. This study provides a new experimental handle on radial-flow fluctuations and their possible collective origin in small collision systems.
Hydrodynamics can describe the thermalized quark-gluon plasma phase of heavy-ion collisions. Extending its validity to pre-equilibrium stages requires accounting for short-lived non-hydrodynamic modes. In this talk, I present a method that retains selected information from these modes to extend the validity of hydrodynamics beyond the conventional hydrodynamic regime. I apply this method to both weakly coupled kinetic theory and strongly coupled holography. In both cases, the nearest-neighbour coupling structure allows higher non-hydrodynamic degrees of freedom to be propagated iteratively into the hydrodynamic mode, extending its regime of validity. This provides a common framework for comparing collective dynamics across microscopically distinct theories.
A central question in strong-interaction physics, governed by quantum chromodynamics (QCD), is whether femto-scale droplets of quark–gluon plasma (QGP) form in small collision systems involving projectiles significantly smaller than heavy ions. Collisions of light ions such as 16O and 20Ne offer a unique opportunity to probe the emergence of collective behavior in QCD matter. This work presents the first measurements of elliptic (v2) and triangular (v3) flow of charged particles in the OO and Ne-Ne collisions at √sNN = 5.36 TeV at the LHC. The hydrodynamic model predictions, explicitly incorporating the nuclear structures of 16O and 20Ne, exhibit a good agreement with the flow measurements presented. The observed increase of v2 in central Ne–Ne collisions relative to OO collisions, driven by the nuclear geometries, highlights the importance of utilizing light nuclei with well-defined geometric shapes to constrain the initial conditions. These findings support the presence of nuclear geometry-driven hydrodynamic flow in light-ion collisions at the LHC.
无中微子双贝塔衰变是目前粒子物理与核物理研究领域的科学前沿，是可能突破粒子物理标准模型的重要研究方向之一 。如果实验上观测到无中微子双贝塔衰变，将提供违反轻子数的直接证据，同时表明中微子是马约拉纳粒子，有助于理解宇宙中正反物质不对称之谜。
其中，NME是连接半衰期与中微子质量的关键“桥梁” ，其数值大小直接决定衰变的快慢，并影响提取中微子质量的精度。然而，不同核理论模型对NME的预测相差三倍甚至更多，对设计以及解释无中微子双贝塔衰变实验带来很大的不确定性。因此，降低候选原子核衰变NME的不确定性是亟需解决的关键科学问题之一。
在近期的工作中，我们计算了¹⁵⁰Nd → ¹⁵⁰Sm 到无中微子双贝塔衰变核矩阵元NME，并进行了母核¹⁵⁰Nd + ¹⁵⁰Nd 之间的高能碰撞模拟。我们发现，NME与高能碰撞中形成的夸克-胶子等离子体（QGP）的空间梯度、各向异性等宏观性质呈现出显著相关性。而这些QGP性质可以通过当前重离子对撞实验中的集体流测量直接获取。这一发现不仅为传统低能核结构研究提供了全新的高能“参照标尺”，也为未来通过高能对撞实验反向约束无中微子双贝塔衰变理论提供了强有力的可能性。研究成果开辟了连接高能核碰撞与低能弱衰变过程的新路径，有望为中微子质量的确定及新物理的探索提供理论支撑。
Relativistic $^{16}$O+$^{16}$O collisions provide a valuable opportunity to study both the quark-gluon plasma formed in small systems and the intrinsic structure of $^{16}O$. Recent implementations of ab initio nuclear configurations in heavy-ion simulations have produced different predictions for cluster-sensitive observables, making it difficult to identify the origin of possible 𝛼-cluster signals. In this work, we introduce a controlled sampling scheme that varies the compactness of 𝛼-cluster-induced multi-nucleon correlations while keeping the one-body density distribution of $^{16}O$ fixed. This allows us to separate effects driven by the tetrahedral one-body density from those driven by genuine multi-nucleon correlations. We show that the normalized ratios Norm($𝑣_2\{2\}/𝑣_2\{4\}$) and Norm($𝑣_2\{2\}/𝑣_3\{2\}$), together with their initial-state eccentricity counterparts, provide complementary constraints on initial-condition model dependence and cluster compactness. Hybrid hydrodynamic simulations and comparisons with recent LHC measurements further clarify the extent to which the initial-state signals survive final-state evolution. Our results provide a framework for using relativistic light-ion collisions to constrain cluster correlations in $^{16}O$.
Traditional Monte Carlo Glauber models[1] treat deformed nuclei using a classical approximation: in each event, a fixed orientation is randomly assigned to the nucleus, which effectively breaks the rotational symmetry. However, for even-even nuclei, the ground state must remain in the $J=0$ ground state. To restore this broken symmetry, we introduce quantum superposition over all possible orientations[2]. This approach ensures the nucleus is correctly described as a symmetry-restored state rather than a classically fixed configuration.
In this talk, we use the same approach[2] to restore the entangled ground state and investigate the impact on final-state observabels in in Ne+Ne, Si+Si, Ru+Ru, and U+U collisions. In addition to the two-particle flow coefficients, $v_n\{2\}$, we investigate the normalized symmetric cumulants (NSCs) and the Pearson correlation which are sensitive to nuclear structure and can be used to constrain nuclear deformation parameters[3].
Our results show that, in central Ne+Ne collisions, $v_2$ is reduced by approximately $13\%$ in the quantum-superposition configuration relative to the classical configuration, and in U+U collisions, the corresponding reduction is approximately $5\%$. Quantum effects are also pronounced in the cross-system ratios of the covariance numerator, which are defined generically as
$
R_{X/Y}
=
\frac{
\left\langle v_2^2\,\delta[p_T]\right\rangle_{X}
}{
\left\langle v_2^2\,\delta[p_T]\right\rangle_{Y}
}.
$
For the strongly deformed prolate systems Ne+Ne and U+U, the corresponding ratios, $R_{\mathrm{Ne+Ne}/\mathrm{O+O}}$ and $R_{\mathrm{U+U}/\mathrm{Au+Au}}$, change from approximately $1.9$ to $0.9$ and from approximately $-3.1$ to $-1.4$, respectively. The above results indicate that considering a symmetry-restored description of the nuclear ground state can have important implications for extracting nuclear-structure information and constraining QGP properties in both light- and heavy-ion collisions.
[1] M.L. Miller, K. Reygers, S.J. Sanders, P. Steinberg, Ann. Rev. Nucl. Part. Sci. 57 (2007) 205.
[2] W. Ke, arXiv:2509.09549 [nucl-th] (2025).
[3] M.I. Abdulhamid, et al. (STAR Collaboration), Nature 635 (2024) 67.
Jet quenching provides a valuable measure of the opacity of the quark-gluon plasma (QGP) produced in high-energy heavy-ion collisions. However, substantial suppression of charged hadron spectra is observed in highly peripheral collisions, despite the expectation of negligible jet-QGP interactions in this regime. In this work, we demonstrate that the suppression observed in highly peripheral collisions is predominantly driven by the dilute nucleon overlap in the initial state, rather than an onset of strong jet-QGP interactions. To quantitatively address this, we develop a HIJING-based initial condition model that accounts for the impact parameter dependence of both inelastic nucleon-nucleon (NN) collisions and the number of hard partonic scatterings per inelastic NN collision. This dependence introduces a geometric bias effect on the jet yield within a given centrality class of nucleus-nucleus (AA) collisions. Furthermore, we incorporate the Linear Boltzmann Transport (LBT) model to simulate jet-QGP interactions, introducing a large $p_{z}$-scheme for fake partons to eliminate unphysical enhancements of the hadron spectrum in peripheral AA collisions. By combining the geometric bias effect obtained from the HIJING-based model and the QGP effect simulated using the LBT model, we achieve a unified description of the charged hadron nuclear modification factor ($R_{AA}$) from central to highly peripheral Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. Our findings highlight the crucial role of initial-state collision geometry in properly interpreting jet quenching observables in small collision systems.
Quarkonia are excellent probes for studying the interactive properties of quark-gluon plasma formed in relativistic heavy-ion collisions. To correctly interpret the observed suppression of quarkonium production in $\text{Au}+\text{Au}$ collisions at $\sqrt{s_{\text{NN}}}$ = 200 GeV, the cold nuclear matter (CNM) effects in $p+\text{Au}$ collisions are quantified by the nuclear modification factor ($R_{p\text{Au}}$), given the long-established presumption that the energy density and the temperature produced in proton-nucleon collisions are insufficient to form QGP droplets. It is defined as the ratio of the yield of the quarkonium in $p+\text{Au}$ collisions to that in $p+p$ collisions, scaled by the average number of binary nucleon-nucleon collisions.
In this presentation, a study of cold nuclear matter (CNM) effects is reported based on STAR measurements of inclusive $J/\psi$ and $\Upsilon$ production in $p+p$ and $p+\text{Au}$ collisions at $\sqrt{s_\text{NN}}$ = 200 GeV. The $J/\psi$ $R_{p\text{Au}}$ is measured as a function of $p_{\text{T}}$, while the $\Upsilon$ $R_{p\mathrm{Au}}$ is measured separately as functions of $p_{\mathrm{T}}$ and $y$, with all other kinematic variables integrated over. The $J/\psi$ $R_{p\text{Au}}$ is consistent with unity, suggesting negligible modification of the yield by CNM effects in this kinematic region, while noticeable suppression for $\Upsilon$ is observed in covered kinematic ranges. Comparisons are made to results from other experiments as well as to model calculations and physics implications will also be discussed.
Entanglement generated in the early stage of relativistic heavy-ion collisions (HIC) is considered a direct and fundamental source for understanding fast thermalization, entropy production, and evolution. Spin entanglement in QCD, arising from non-commutative geometric effects of quantum fields, provides a new avenue to explore the quantum informational footprint of the QCD topological vacuum structure and reveal potential origin of thermal entropy in chromodynamics. This work studies spin entanglement among quarks originating from two main sources: instanton(sphaleron)-induced effects, and gluon–quark scattering. Innovatively, we provide a method to extract spin entanglement in scattering processes respectively for light and heavy quark sector that corresponds to the two sources. We systematically calculate the entanglement in both cases and present results including concurrence and entropy as functions of the instanton parameter, physical mass, and momentum scale—aspects not explicitly discussed in previous studies. This directly reveals how the non-equilibrium nature of the system and field topology effects modulate spin entanglement, and clarifies the corresponding quantitative relationship between entanglement measures and core physical information related to flavor and scale. More importantly, this quantitatively explains the well-know sphaleron effect on QGP formation in early stage and its fast thermalization from spin d.o.f.
We further interpret the entanglement time scale, providing a quantitative comparison with the scrambling time, and clarify the quantum informational relations in the early-stage thermalization. Finally, we discuss some recent experimental interests and results in high-energy collisions.
Jets produced in heavy-ion collisions interact with the hot and dense quark–gluon plasma, leading to parton energy loss, redistribution of jet energy, and possible broadening of the jet direction. The azimuthal correlation between a high-pT trigger hadron and recoil jets provides a sensitive probe of these medium-induced modifications.
In this contribution, we present measurements of semi-inclusive charged-jet distributions recoiling from a high-pT trigger hadron in pp and central Pb–Pb collisions at 5.02 TeV with ALICE. A data-driven subtraction technique is used to suppress the large uncorrelated background, enabling measurements over a broad range of jet transverse momentum, azimuthal angle, and jet resolution parameter (R), including the low-pT region. The recoil-jet yield and acoplanarity distributions in Pb–Pb collisions are compared with those in pp collisions to investigate jet suppression, energy redistribution, and medium-induced azimuthal broadening. The dependence of these effects on jet pT and R, together with comparisons to theoretical model calculations, provides further insight into jet–medium interactions and the response of the QGP.
Ultra-peripheral Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\mathrm{NN}}}=200~\mathrm{GeV}$ at RHIC provide a controlled setting for investigating nuclear-structure effects in the photonuclear production of forward neutrons. Although the two isobars have the same mass number, they differ in proton number and photonuclear response, making their neutron-tagged Coulomb-dissociation cross-section ratios sensitive to effects beyond simple electromagnetic-flux scaling. In this talk, we present impact-parameter-dependent equivalent-photon calculations for single and mutual Coulomb dissociation,
including exclusive and inclusive neutron-emission channels. We examine how the Ru/Zr ratios vary among different neutron topologies for single and mutual dissociation. The calculations reveal a pronounced channel dependence which exclusive low-multiplicity neutron channels exhibiting stronger isobar sensitivity than inclusive neutron-emission channels. These results demonstrate the potential of neutron-tagged Coulomb dissociation as a probe of isobar-dependent photonuclear response.
Directed flow $v_1$ has been used to probe the early dynamics in high-energy nuclear collisions. The vector meson $\phi(s\bar{s})$, with a mass comparable to that of light baryons and weak hadronic interactions, provides a unique probe of the interplay between particle production mechanisms and early-stage dynamics in high-density nuclear matter.
In this talk, we report measurements of $\phi$-meson directed flow ($v_1$) in Au+Au collisions at center-of-mass energies of 3.0, 3.2, 3.5, 3.9, and 4.5~GeV, using data collected by the STAR experiment as part of the RHIC Beam Energy Scan II program. These energies correspond to the high-baryon-density region of the QCD phase diagram, with baryon chemical potentials of $\mu_B \approx 590$--$760$~MeV. In this region, the measured $\phi$-meson $v_1$ exhibits a positive slope with a magnitude comparable to those of baryons, such as protons and $\Lambda$, while the directed flow of lighter mesons, including pions and kaons, is significantly smaller. The results are compared with UrQMD transport model calculations, providing insights into the role of baryon-resonance contributions and strange-hadron transport in dense QCD matter.
Recent work has proposed sequential hadronization of open-charm hadrons in the quark-gluon plasma, wherein more tightly bound species such as Ds+ form earlier near 1.2Tc and D0 forms later at Tc. That work showed that this mechanism naturally reverses the sign of the D0 − Ds+ elliptic-flow splitting ∆v2 ≡ v2(D0) − v2(Ds+) relative to the conventional simultaneous baseline. In this work, we demonstrate that event-shape engineering (ESE) provides a sharper discrimination
between the two pictures than inclusive measurements alone. By selecting large-q2 and small-q2 events in 0–10% and 30–50% centrality classes in Pb–Pb collisions at √sNN = 5.02 TeV, we show that the geometry-driven enhancement of charm-meson v2 can be separated from the hadronization-time response: the positive ∆v2(D0 − Ds+) in the sequential scenario grows systematically with q2,while the corresponding response slope χ reveals a species-dependent hierarchy χ(D0) > χ(Ds+) that is robust against the overall flow normalization and absent in the simultaneous baseline. In the simultaneous case, the splitting is near zero or negative and does not follow the same geometry scaling. Notably, the semi-central 30–50% class emerges as the optimal window, because the non-monotonic interplay between QGP lifetime and initial eccentricity maximizes the late-stage flow conversion. The Ds+/D0 yield ratio and its q2 double ratio remain close to unity, confirming that the splitting is a dynamical flow effect rather than a chemical yield modification. These results establish ∆v2(D0 − Ds+) and the response slope χ under ESE as complementary differential probes of the space-time structure of charm hadronization near the QCD transition temperature.
Measurements of identical pion femtoscopy offer insights into collision dynamics, such as collective expansion, geometry of the collision zone at freeze-out, final state interactions, etc. In addition to the quantum interference and Coulomb interactions among the pion pairs, Coulomb interactions between the pair and the net positive charge in the emitting source affect the final correlation measurements as well. Furthermore, due to the imbalance of protons and neutrons inside the colliding nuclei, initial isospin, which could play an important role in determining the Equation of State (EoS) of the produced medium, also can affect the correlation functions at high baryon density.
In this talk, we present the results of the identical charged pion correlations from $\sqrt{s_\mathrm{NN}}$ = 3.0, 3.2, 3.5, 3.9, 4.5, 7.7 GeV Au+Au collisions collected by the STAR experiment. A new procedure has been developed to remove the residual effect from the 3rd-body Coulomb force. The HBT radii ($R_{\mathrm{out}}, R_{\mathrm{side}}, R_{\mathrm{long}}$) extracted from the positive and negative charged pion correlation functions, before and after removing the 3rd-body Coulomb effect, will be presented as a function of collision energy. Transport model UrQMD calculations with realistic experimental cuts will be used to aid the discussions.
This report investigates the infrared structure of QCD through the lens of the Cho–Faddeev–Niemi decomposition and Faddeev–Niemi effective theory. We argue that gluon knots, as topological solitons characterized by the Hopf invariant, constitute the relevant infrared ground-state degrees of freedom of Yang–Mills fields. Within this framework, we present a unified mechanism for monopole condensation and center-vortex confinement. Crucially, we introduce a picture of baryons as quarks embedded in a gluon-knot background, where dual superconductivity naturally gives rise to the characteristic $\mathrm{Y}$-shaped flux-tube geometry. We further delineate how the strong local color-magnetic fields drive chiral symmetry breaking through magnetic catalysis. The talk will also highlight the topological connection between the Hopf invariant, Yang–Mills vacua, and the axial anomaly, demonstrating that the topological current of gluon knots offers a viable carrier for the missing proton spin. Ultimately, we offer a cohesive, topology-driven perspective uniting confinement, chiral symmetry breaking, and baryon structure.
The energy-energy correlator (EEC) provides a powerful probe of jet substructure and multi-scale parton dynamics. A key challenge in jet quenching physics is to consistently model the transition between vacuum-like parton shower evolution at high virtuality and subsequent jet-medium interactions. Within the LIDO framework, this physics is governed by a critical cutoff scale $Q_0$ that separates high-virtuality vacuum-like splittings from subsequent medium-induced transport.
In this work, we use the LIDO hard parton transport model coupled to a simple ansatz for jet induced hydrodynamic response of the medium to study medium-modified parton showers via the EEC, with a particular emphasis on elucidating the impact of this vacuum-medium transition scale. We demonstrate that jet suppression exhibits markedly different sensitivities to the transition scale $Q_0$ between vacuum-like and medium-induced parton showers.
After calibrating the LIDO model to the jet $R_{AA}$, we first systematically investigate the impact of various model parameters on the energy-energy correlator (EEC). We find a pronounced dependence of the EEC on $Q_0$, demonstrating that its angular structure is highly sensitive to the modeling of the vacuum-medium transition and establishing the EEC as a promising observable to constrain the onset of medium effects in jet evolution. Guided by these insights, we further extend our study to investigate the EEC distributions and their ratios with respect to the p--p baseline across different collision systems, specifically in Pb--Pb ($\sqrt{s_{\mathrm{NN}}} = 5.02$~TeV), p--Pb ($\sqrt{s_{\mathrm{NN}}} = 5.02$~TeV), and O--O ($\sqrt{s_{\mathrm{NN}}} = 5.36$~TeV) collisions.
Understanding the internal structure of the proton—including its mass spectrum, structure functions, and electromagnetic and gravitational form factors—remains a central challenge in hadronic physics. While lattice QCD and experimental measurements provide valuable insights, holographic methods are a meaningful complementary tool. Here, we employ different holographic approaches to calculate these quantities. Specifically, we use the VQCD model and the modified soft-wall model to study the mass spectrum and form factors, obtaining results consistent with experimental data and lattice QCD calculations. In addition, we employ the J/ψ production cross section to extract the trace anomaly contribution to the proton mass, yielding a value of approximately 24%, which also agrees with lattice QCD findings. This work highlights the power of holography as a complementary tool for probing the proton's internal structure from both classical and quantum-gravity-inspired perspectives.
base on Jiali Deng and Defu Hou: Phys.Rev.D 112 (2025) 3, 036011; Phys.Rev.D 114 (2026) 2, 026013; arXiv:2512.17554, EPJC(2026) in press
喷注是硬散射过程产生的高能部分子强子化后的准直粒子束流，是检测微扰量子色动力学的重要探针。在重离子碰撞中，部分子喷注穿过夸克-胶子等离子体（QGP）时发生能量损失，这一现象被称为喷注淬火。除喷注本身的能量损失外，部分子沉积到介质中的能量与动量还会激发局域介质的响应，形成所谓的喷注耗散尾流效应。理论上，这种介质响应包含两种主要成分：沿喷注方向传播的马赫锥声波激发，以及在喷注反方向上因动量守恒导致的粒子产额耗尽，即耗散尾流。耗散尾流作为喷注-介质相互作用的独特信号，近年来受到理论和实验的高度关注。最新研究进展表明，CMS通过双喷注的关联测量显示了耗散尾流效应的相关信号，ALICE合作组亦计划在LHC第三期运行取得的数据中开展相关研究，以补充和完善CMS的相关策略，深入理解该实验现象的物理机制。
为给上述上述研究提供ALICE接受度范围内的基线测量，本研究利用PYTHIA事件产生器模拟了质子-质子碰撞中的双喷注事件，系统考察了不同参数开关、双喷注选择偏好、横动量区间以及赝快度接收范围等调谐因素对双喷注-强子关联快度不对称性的影响。通过大规模事件样本，首先重现了CMS实验中的相关策略，并给出了ALICE探测器条件下的双喷注关联测量中的运动学截断敏感区域，量化了该观测量在纯QCD背景下的本征涨落与系统偏差，为未来在ALICE实验中识别喷注诱导扩散尾迹信号提供了必要的基准参照。
We construct a light-front Hamiltonian description of the nucleon in an enlarged low-energy Fock space containing the valence $q q q$ sector, the sea-flavor $q q q q \bar{q}$ sector, and the gluonic hybrid $q q q g$ sector. The $q q q \leftrightarrow q q q q \bar{q}$ mixing is taken to be generated by the chiral pair of $\sigma$ - and $\pi$-type operators used in the nucleon-pentaquark analysis, while the $q q q \leftrightarrow q q q g$ mixing is generated by a twist-3 colorelectric operator. It induces electric-dipole transition between a color-singlet nucleon and a coloroctet three-quark core coupled to a transverse constituent gluon. We summarize the Young-tableau structure of the Pauli-allowed pentaquark and hybrid bases, derive the light-front matrix elements, and write the dressed nucleon as a normalized superposition of the three sectors. The construction makes explicit how flavor-sea and gluon-sea components enter the same Hamiltonian eigenstate and provides a starting point for computing parton distributions, form factors, and transition amplitudes at a hadronic matching scale.
Confirming gluon saturation at the Electron--Ion Collider requires observables sensitive to saturation-induced transverse structure that survive hadronization. We present an event generator implementing folded small-$x$ evolution for proton and gold targets, connecting nonlinear gluon dynamics to exclusive final states through complete shower and hadronization. Angular energy flow and leading-hadron azimuthal decorrelation show weak sensitivity to saturation dynamics, diluted by remnant fragmentation and hadronization effects. In contrast, a collective Breit-frame vector recoil provides a measured Au/proton ratio and a conditional proton-referenced inference of nuclear broadening. Comparisons between Pythia string fragmentation and Herwig cluster hadronization show that the inferred nuclear broadening depends only weakly on the hadronization model. Exact common-hard-state and full-event response-transfer tests separate the shared fragmentation kernel from target-dependent ISR, remnant, and color-flow effects. This provides a controlled route to test whether multiparticle correlations retain saturation information at EIC energies where dijet reconstruction becomes unreliable.
The search for quark–gluon plasma (QGP)-like collectivity in small collision systems remains a central goal of high-energy nuclear physics. Recent results from O$+$O collisions suggest that strongly coupled, near-perfect-fluid behavior may emerge even in such small systems, motivating a detailed investigation of jet quenching in systems of reduced size. In this work, we study hadron and jet suppression in O$+$O collisions at the LHC energy $\sqrt{s}=5.36$ TeV to systematically quantify jet energy loss within the Linear Boltzmann Transport (LBT) model, coupled to CCNU-LBNL viscous (CLVisc) (3+1)D hydrodynamic background. We further investigate jet energy loss in O$+$O collisions at RHIC energy $\sqrt{s} = 200$ GeV, enabling a unified comparison of jet suppression across different energy scales. Finally, by comparing the O$+$O results with corresponding Pb$+$Pb calculations, we examine the path-length dependence of jet quenching and assess how medium size governs the observed suppression.
Jet quenching provides a sensitive probe of the transport properties and microscopic structure of the quark-gluon plasma (QGP). In this work, we use the Linear Boltzmann Transport (LBT) model to study jet-medium interactions from two complementary perspectives: photon-tagged jet observables in different collision systems and multi-point energy correlators inside jets.
The first part focuses on photon-tagged jet production and modification. We validate the LBT calculation with CMS measurements of photon-tagged jets in Pb+Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV, including the momentum imbalance $x_{J\gamma}$, the associated-jet yield modification $I_{\rm AA}^{\rm jet}$, and the azimuthal correlation $\Delta\phi_{J\gamma}$. The associated-jet transverse-momentum spectrum and the parton-level $\Delta p_T$ are used as model diagnostics to connect the observed imbalance and yield suppression to jet energy loss and medium response. With the same transport setup, we then provide predictions for photon-tagged jet observables in O+O collisions at $\sqrt{s_{\rm NN}}=5.36$ TeV. The results show that O+O exhibits a visible but weaker pattern of jet energy loss and yield modification than Pb+Pb. We further study the jet profile $\rho(r)$ and the energy-energy correlator (EEC) of photon-tagged jets to resolve the internal angular redistribution of jet energy. The EEC ratio shows small-angle suppression and large-angle enhancement, with a weaker modification in O+O than in Pb+Pb. The crossing angle of the EEC ratio decreases with increasing photon transverse momentum, consistent with the expectation that the relevant angular scale is tied to the hard jet scale.
The second part studies the three-point energy correlator (E3C) as a more differential probe of jet substructure modification. After validating the calculation against the two-point EEC results, we examine E3C edge distributions and the full $(\xi,\phi)$ shape space in both vacuum and medium-modified jets. The AA/pp ratio of the E3C shows that the medium modification is not uniform over the three-particle geometry, but is enhanced in configurations sensitive to broad-angle correlations and medium response. To identify the origin of this structure, we decompose the partonic E3C into contributions from shower partons, medium-induced radiated gluons, and jet-induced medium response. This decomposition shows that radiation-related and medium-response-related triplets populate different regions of the E3C shape space, providing a way to separate perturbative shower modification from wake-like medium response.
Together, these studies use the same LBT framework to connect conventional photon-tagged jet observables with energy-correlator-based jet substructure measurements. The photon-tagged jet analysis constrains the overall energy-loss phenomenology and extends it to O+O predictions, while the EEC and E3C analyses probe the angular pattern and microscopic origin of the medium modification inside jets.