Spicy Gluons (胶麻) 2025: Workshop for Young Scientists on the quark-gluon matter in extreme conditions

31 Jul 2025, 08:00 → 4 Aug 2025, 23:00 Asia/Shanghai

Zhenyu Chen (Shandong University (CN))

The 2nd edition of Spicy Gluons (胶麻) Workshop for Young Scientists on the quark-gluon matter in extreme conditions will be held July 31 - August 4, 2025 in Aoshan Bay, Qingdao, China. Spicy food is known to stimulate the senses and taste. The love of the spiciness also symbolizes the fiery passion of the youth. Likewise, the goal of the Spicy Gluon workshop is to stimulate the sense and taste of early career scientists in the field by cooking, presenting and tasting flavored works with fiery passion. The lovers of Spicy Gluon are highly encouraged to submit your recipe (aka. abstract) and pre-register. If the abstract is accepted, you will be invited to join the workshop. The workshop will guarantee every accepted abstract to be an oral presentation and cover the local expenses (hotel + food). The workshop emphasizes discussion, collaboration, and innovation. All the participants are expected to stay for the whole workshop and actively contribute to the discussion session.

第二届“胶麻”青年科学家研讨会将于2025年7月31日-8月4日在中国青岛鳌山湾举办，旨在为年轻科学家们搭建一个交流与学术展示的平台。辣味美食以其刺激感官和味蕾的独特特点而享誉盛名，也象征着年轻人的热情和活力。与此类似，胶麻研讨会致力于通过火辣的烹饪、展示和品尝科研成果，激发领域初出茅庐的科学家们的感官与思维。我们热情鼓励所有对胶麻研讨会感兴趣的青年学者们积极提交报告摘要并进行预注册。一旦摘要被接受，您将被邀请参加研讨会，会议主办方将提供全程食宿。我们将确保每个摘要都能得到口头报告的机会，并强调学术讨论、合作与创新。我们期待着所有参与者全程积极参与，并为学术讨论环节做出重要贡献。

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。

The topics of the workshop contain but are not limited to:

研讨会内容包括但不限于:

QCD相变与状态方程(QCD phase transition and equation of state)
重味与奇异粒子(heavy flavor and strangeness)
自旋极化和手征效应(spin polarization and chiral effect)
喷注物理(jet physics)
核子结构(nucleon structure)
电磁信号(electromagnetic signal)
UPC物理(UPC physics)
EIC/EicC物理（EIC/EicC physics）
集体流和关联(collective flow and correlation)
新的理论方法(new theoretical methods)
核物理中的机器学习（Machine learning in nuclear physics)
量子计算（Quantum Computing）
核天体物理 （Nuclear Astrophysics）

The workshop will be 3 full days August 1-3, 2025

会议日程为8月1日-3日3整天

Abstract submission is included in the registration form

摘要提交通过注册表完成

会议费用（Conference fee）：
The registration fee is 500 yuan per person, inclusive of accommodation, meals, and refreshments. Transportation costs are not included and are the responsibility of the participants.

注册费500元/人，包含食宿费用和茶歇，交通费用自理。

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Thursday 31 July

Registration

Friday 1 August

1 Welcome

Speaker: Zhenyu Chen (Shandong University (CN))

2 Probing Small-x Nuclear Structure via Photoproduced Vector Mesons in UPCs

Speaker: Zaochen Ye (South China Normal University)

Probing-Nuclear-Structure-via-VMs-in-UPCs-ZaochenYe-SpicyGluons2025-v2.pdf

3 Probing gluon structure with J/ψ photoproduction in isobaric ultra-peripheral collisions at 200 GeV with STAR

In ultra-peripheral collisions (UPCs), coherent J/ψ photoproduction has been recognized as one of the most sensitive probes of the nuclear gluon distribution. The collision system size in isobaric collisions Ru + Ru and Zr + Zr lies between d + Au and Au + Au collisions. Therefore, the measurement of coherent J/ψ photoproduction in isobaric UPCs offers a unique opportunity to study the system size dependence of gluon structure. In this talk, we present the differential cross sections of photoproduced coherent J/ψ as a function of rapidity (y) in isobaric UPCs at 200 GeV. These data provide crucial constraints on the system size dependence of the gluon structure function within nuclei in the kinematic range x_parton, the momentum fraction carried by the gluon, ~0.015−0.03. The results are compared with STARlight and previous STAR measurements. Physics implications are also discussed.

Speaker: Zengzhi Li

10:20 Coffee

4 Calculations of Di-Hadron Production via Two-Photon Processes in Relativistic Heavy-Ion Collisions

Two-photon processes in relativistic heavy-ion collisions have emerged as a critical probe of quantum electrodynamics in ultra-intense electromagnetic fields, with recent focus extending beyond dileptons to hadronic final states. However, at present, quantitative studies of di-hadron production via two-photon interactions remain scarce. We employ the Equivalent Photon Approximation to obtain differential cross-section predictions for $\pi^{+}\pi^{-}, K^{+}K^{-}$, and $p\bar{p}$ pairs produced in ultra-peripheral $\mathrm{Au{+}Au}$ collisions at $\sqrt{s_{NN}} = 200\,\text{GeV}$ within the STAR acceptance，using experimental input from previous measurements at electron-positron colliders to model the two-photon production cross sections for these final states. The calculations deliver the unified baseline for light-meson and baryon pairs in this environment, supplying benchmarks for upcoming STAR measurements and guiding future systematic investigations of hadronic two-photon processes at RHIC and LHC facilities.

Speaker: Luobing Wang

5 Rescattering effects on spin-interference for rho0 photoproduction in heavy-ion collisions

Recent measurements by various experiments in ultra-peripheral collisions have observed spin-interference in $\rho^{0}$ photoproduction, marking a breakthrough in Fermi-scale quantum interference experiments. Building on this, STAR extended the measurement to hadronic heavy-ion collisions, where significant rescattering effects on $\rho^{0}$ mesons were expected. In this study, we investigate how these rescattering effects influence the measurement of spin-interference. By embedding $\rho^{0}$ mesons produced via photoproduction, modeled by the Vector Meson Dominance model, into the Ultrarelativistic Quantum Molecular Dynamics framework, we estimate the impact on the $\cos 2\phi$ and $\cos 24\phi$ modulations, where $\phi$ is the angle between $\rho^{0}$ and one of the daughters’ ($\pi^{\pm}$) transverse momentum. The results indicate a significant suppression of the $\cos 2\phi$ modulation, while the $\cos 4\phi$ modulation remains largely unaffected, which provides insight for understanding the difference due to rescattering effects between experimental measurements and theoretical predictions for $\rho^{0}$ photoproduction in heavy-ion collisions.

Speaker: Yusong Wang

6 Very low pT e+e- pair and Jpsi production in isobaric collisions

Speaker: Kaifeng Shen (University of Science and Technology of China)

7 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

12:15 Lunch

8 Deciphering the spatial and spin structures of (anti-)hypertriton in heavy-ion collisions

The hypertriton($_\Lambda^3$H), a bound state of a proton, a neutron, and a $\Lambda$ hyperon, serves as a unique probe for studying hyperon-nucleon interactions and the behavior of strange quarks in dense nuclear matter. In heavy-ion collisions, the binding energy and spin of $_\Lambda^3$H have been experimentally measured, albeit with significant uncertainties. We propose a novel method to extract detailed information about their wave function by analyzing the production and transverse momentum ($p_T$) spectrum of (anti-)hypertritons using the coalescence model. Furthermore, light hypernuclei can also be polarized in non-central heavy-ion collisions, similar to unstable hadrons. We suggest that the global polarization of (anti-)hypertritons can be utilized to decipher their internal spin structures in heavy-ion collisions. This study not only provides a understanding of the spatial and spin structures of (anti-)hypertritons but also offers new insights into the dynamics of hyperon-nucleon interactions and the polarization mechanisms in heavy-ion collisions.

Speaker: Daineng Liu

9 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

10 Influence of the residual magnetic field on the azimuthal distribution of final-state particles in photon-nuclear processes

In relativistic heavy-ion collisions, charged particles are accelerated to nearly the speed of light, and their external electromagnetic fields can be effectively approximated as quasi-real photons. These photons interact with another nucleus via photon-nuclear interactions, producing vector mesons. These vector mesons possess extremely low transverse momentum ($p_T\sim0.1$ GeV/$c$), distinguishing them from particles produced via hadronic interactions. STAR and ALICE have observed $J/\psi$, $\rho^0$ and other vector mesons with very low $p_T$, which are well described by photoproduction models. This unique characteristic of having extremely low transverse momentum allows them to serve as a novel experimental probe. Recent STAR results show that the equivalent photons in photoproduction processes are fully linearly polarized, affecting the azimuthal distribution of final-state particles like $\rho^0 \rightarrow \pi^+ \pi^-$. Since the polarization links to the initial collision geometry, the $\rho^0$ azimuthal modulation can probe nuclear structure. However, the post-collision magnetic field may deflect these particles, distorting the azimuthal distribution and complicating structure measurements. We simulated the distribution of residual magnetic fields over time under different collision conditions using UrQMD for Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV and calculated their effects on the azimuthal modulation ($\left$) of photoproduced $\rho^0$. Our results show that in peripheral collisions, the field significantly alters the $\left$ for photoproduced $\rho^0$ with $p_T\approx$ 0.1 GeV$/c$. This provides key insights for future nuclear structure studies via photoproduction in peripheral collisions.

Speaker: Zhan Zhang

11 The study of Double-spin asymmetry in SIDIS process at CLAS12, COMPASS and EicC

We investigate the longitudinal-transverse double-spin asymmetry in the semi-inclusive deep inelastic scattering(SIDIS) for Lambda hyperon production by scattering a longitudinally polarized beam off a transversely polarized proton target. With the transverse momentum of the final hadron is integrating out, we predict the asymmetry with a modulation for the Lambda hyperon production. We take into account both contributions to predict the asymmetry at the kinematics of CLAS12, COMPASS and EicC. We find that the asymmetry in Lambda hyperon production SIDIS process are sizable. In addition, we consider the contribution of sea quarks to the asymmetry within the kinematics of CLAS12, COMPASS, and EicC. The result shows that the asymmetries are larger when sea quarks are included, and the contribution of sea quarks to the asymmetry mainly comes from the convolution of the transversity distribution function h_1(x) and the twist-3 chiral-odd FF tilde E(z). It shows that the measurement of the asymmetry in Lambda hyperon production SIDIS process can provide an effective way to access the contribution of the twist-3 FF tilde E(z) of Lambda hyperon.

Speaker: Keyang She

15:25 Coffee

12 Measurement of transverse polarization of Lambda/anti-Lambda inside jets in unpolarized pp collisions at 200 GeV

Speaker: Taoya Gao (Shandong University)

13 Chiral Properties of (2+1)-Flavor QCD in Strong Magnetic Fields at Zero Temperature

We present a lattice QCD study of chiral condensates, light and strange pseudoscalar meson masses and decay constants in the presence of strong background magnetic fields. Our simulations employ (2+1)-flavor ensembles with physical quark masses, generated using the highly improved staggered quark (HISQ) action. To enable a controlled continuum extrapolation, we employ four lattice spacings ($a \approx$ 0.056, 0.067, 0.084, 0.112 fm). Seven different magnetic field strengths are considered, reaching up to $ \sim 1.22 \mathrm{GeV}^2 ( \sim 66 M_\pi^2$ ) in the vacuum. Meson masses and decay constants are extracted from the exponential decay and amplitudes of two-point correlation functions. We analyze their dependence on the magnetic field and discuss the implications for chiral symmetry breaking and the internal structure of mesons in strong magnetic backgrounds.

Speaker: Dan Zhang

14 Bayesian inference of the magnetic field and chemical potential on holographic jet quenching in heavy-ion collisions

"Jet quenching is studied in a background magnetic field and a finite baryon chemical potential. The production of energetic partons is calculated using the next-to-leading order (NLO) perturbative Quantum Chromodynamics (pQCD) parton model, while the parton energy loss formula is obtained from the AdS/CFT correspondence incorporating the magnetic field and baryon chemical potential effects.
Using Bayesian inference, we systemically compare the theoretical calculations with experimental data for the nuclear modification factor $R_{AA}$ of the large transverse momentum hadrons in different centralities of nucleus-nucleus collisions at 0.2, 2.76 and 5.02 TeV, respectively.
The form of the holographic calculation leads to a strong negative correlation between the magnetic field and the chemical potential for a fixed amount of energy loss. This degeneracy can also be observed after the model calibration. Finally, we discussed the sensitivity of jet quenching phenomena to the enteral magnetic field and a background baryon chemical potential."

Speaker: Liqiang Zhu

15 Baryon electric charge correlation as a magnetometer of QCD

"We present the first lattice QCD results of quadratic fluctuations and correlations of conserved charges in (2+1)-flavor lattice QCD in the presence of a background magnetic field. The simulations were performed using the Highly Improved Staggered Quarks with physical pion mass $m_\pi$ = 135 MeV on $N_\tau=8$ and 12 lattices. We find that the correlation between net baryon number and electric charge, denoted as $\chi^{\rm BQ}_{11} $, can serve as a magnetometer of QCD. At pseudocritical temperatures the $\chi^{\rm BQ}_{11}$ starts to increase rapidly with magnetic field strength $eB \gtrsim 2M^2_{\pi}$ and by a factor 2 at $eB\simeq 8 M^2_{\pi}$.

By comparing with the hadron resonance gas model, we find that the $eB$ dependence of $\chi^{\rm BQ}_{11}$ is mainly due to the doubly charged $\Delta$(1232) baryon. Although the doubly charged $\Delta$(1232) could not be detected experimentally, the proxy constructed from its decay products, protons and pions, retain the $eB$ dependence of $\Delta$(1232)’s contribution to $\chi^{\rm BQ}_{11}$. Additionally, under the same kinematic cuts as in the ALICE experiment, the proxy for $\chi^{\rm BQ}_{11}$ still exhibits a strong dependence on the magnetic field.

Furthermore, the ratio of electric charge chemical potential to baryon chemical potential, $\mu_{\rm Q}/\mu_{\rm B}$, shows significant dependence on the magnetic field strength and varies with the ratio of electric charge to baryon number in the colliding nuclei in heavy ion collisions. These results provide baselines for effective theory and model studies, and both $\chi^{\rm BQ}_{11}$ and $\mu_{\rm Q}/\mu_{\rm B}$ could be useful probes for the detection of magnetic fields in relativistic heavy ion collision experiments as compared with corresponding results from the hadron resonance gas model."

Speaker: Jin-Biao Gu

16 Symmetry and QCD Thermalisation

"In ultra-relativistic heavy-ion collisions, the tremendous energy density temporarily exceeds the QCD confinement scale, deconfining quarks and gluons into a strongly coupled quark–gluon plasma that quickly thermalises and flows like a near-perfect liquid. QGP (QCD) thermalisation in the early stage is a crucial question. We start from a new perspective—intrinsic symmetry—and demonstrate its subtle relation to quantum thermalisation, providing further insight into the QGP’s early dynamics.
We focus on constructing the concept of entropy in quantum field theory, which is essential for understanding thermalisation and the emergence of the second law of thermodynamics in many-body quantum systems. Interestingly, we introduce a symmetry originating from bipartite entanglement, described by the topological group E (represented on Fock space), which directly generates the definition of a generalised entropy H. We then prove the connection between H-production and the eigenstate thermalisation hypothesis (ETH). Finally, by building a quantum-link model of Yang-Mills theory with Wilson quarks, we demonstrate the thermalisation process quantitatively and interpret the accompanying phenomena concerning deconfinement and chiral symmetry ."

Speaker: Chenxi Liang

18:00 Dinner

17 Heavy flavor physics in heavy ion collisions

Speakers: Zebo Tang (University of Science and Technology of China), Zebo Tang (University of Science and Technology of China (CN)), Shuai Yang (South China Normal University)

quarkonium_in_HIC.pdf

Saturday 2 August

18 An extension of the Bargmann-Michel-Telegdi equation from spin hydrodynamics

Speaker: Shi Pu

19 Onset of hydrodynamics in a strongly coupled system based on quantum many-body calculation

"Onset of hydrodynamics in the hot medium created in relativistic heavy-ion collisions is a crucial theoretical question. Addressing this problem in a first-principle manner, requires a real-time, non-perturbative simulation of a large scale quantum system, as hydrodynamic behavior emerges only when approaching the continuum limit. The exponentially large Hilbert space of quantum states prevents an exact simulation on classical hardwares. To overcome such a difficulty, we perform such a simulation using the Tensor Network method, which enables simulations of a reduced representation space of large scale quantum many-body systems by keeping only the most essential quantum states contributing to macroscopic quantities.

We focus on the massive Schwinger model, a low-dimension analog of quantum chromodynamics (QCD), as it shares the important properties such as confinement and chiral symmetry breaking. Starting from an initial quantum state that mimics hard particle collisions, we observe the onset of hydrodynamic behavior that is consistent with the Bjorken-flow in all hydrodynamic degrees of freedom: energy density, fluid velocity, and bulk pressure. The time scale for the onset of hydrodynamics is found to be consistent with the thermalization time of the quantum distribution function. Both time scales are of the same order as the hydrodynamization time determined by fitting the experimental data, upon a physical matching that extrapolates the 1+1 dimensional Schwinger model to the 3+1 dimension QCD."

Speaker: Haiyang Shao

10:20 Coffee

20 Analytical Solution of the Relativistic Boltzmann Equation

We provide an exact analytical solution to the nonlinear relativistic Boltzmann equation for a homogeneous, anisotropically scattering massless gas. Utilizing a BKW-like trial solution, we cast the Boltzmann equation into a set of nonlinear coupled equations for scalar moments, based on which the analytical solution is derived. We also show that this analytical solution admits a stable fixed point corresponding to the equilibrium solution as long as the parameters are physically feasible. Furthermore, a clear correspondence between our solution and the BKW solution pertaining to nonrelativistic Maxwell molecules is established, thereby clarifying the non-existence of a BKW- type solution in the relativistic domain for massive particles.

Speaker: Jin Hu

21 The correlation functions of relaxation time approximation thoery with global current

In this work, we extract the correlation functions of relaxation time approximation theory with global current. The physical system is supposed to be equilibrium before the perturbation imposed to the system. Employing the analytical scheme developed by Paul Rotmasche, we figure out the correlation functions of RTA theory with global current. The discussion of the results is focused on the analytical structure of these retarded correlation functions.

Speaker: Qiuze Sun

22 Shear and bulk viscosities of gluon plasma across the transition temperature

"Shear and bulk viscosities are two key transport coefficients that characterize the fundamental properties of quark-gluon plasma. They quantify the response of the energy-momentum tensor to shear flow and divergent flow, serving as crucial input parameters for the phenomenological and transport models that interpret experimental data, such as the elliptic flow $v_2$.

However, calculating these inherently non-perturbative viscosities within lattice QCD presents challenges due to strong ultraviolet fluctuations in the relevant operators. The traditional approach using the multi-level algorithm is highly effective in suppressing UV fluctuations but is limited to the quenched approximation. Recently, the gradient flow method was introduced to address this issue [1], opening the path to full QCD studies. However, Ref. [1] examined only a single temperature, $1.5T_c$.

This work extends the Ref. [1]'s results to a wide temperature range from $0.76T_c $ to $2.25T_c $, focusing on the high-temperature regime while also probing the system's behaviour across the phase transition. The former enables a fair comparison with the next-to-leading-order perturbative estimates which become more reliable at high temperatures, while the latter allows us to study the system's critical dynamics—a topic of wide community concern. The methodology developed in this work provides the foundation for future full QCD calculations.

Reference:
[1] L. Altenkort, A.M. Eller, A. Francis, O. Kaczmarek, L. Mazur, G.D. Moore, and H.-T. Shu, Phys. Rev. D 108, 014503 (2023)."

Speaker: Cheng Zhang

23 Differentiating Energy-Energy Correlators with Charged Particle Multiplicities within a Jet

Recent CMS results reveal that jets with extremely high multiplicity exhibit novel substructure patterns not seen in ordinary jets, including long-range correlations. However, standard Monte Carlo tools struggle to access this regime due to its rarity and complexity. In this work, we develop a theoretical framework to study high-multiplicity jets, incorporating both multiplicity evolution and Energy-Energy Correlators (EEC) as key probes of jet substructure. Using the normalized multiplicity ratio m=n/⟨n⟩, we investigate how jet properties evolve across multiplicity classes and compare our findings with Pythia8 simulations. This provides new insights into perturbative QCD dynamics in extreme jet events.

Speaker: Pi Duan

12:15 Lunch

24 Tracking the baryon quantum number in heavy ion collisions with the STAR experiment and UrQMD model

In QCD, the baryon number is a conserved quantity that is conventionally assumed to be distributed evenly among valence quarks. An alternative theory suggests that the baryon number may be carried by a non-perturbative topology of gluons, known as the baryon junction, which has a different distribution than valence quarks. Since the charge is carried by the quarks, the theory can be tested by examining the net-baryon and net-charge produced in heavy-ion collisions. The dataset of Ru+Ru and Zr+Zr at √sNN = 200 GeV presents a good opportunity for such a test. Meanwhile, the results in the UrQMD model will provide a reference based on traditional assumptions. The ratio of net baryon to net-charge difference between the two isobaric collisions is found to be significantly larger in experimental data than in UrQMD model. This poses a challenge to the traditional hypothesis of baryon number. In collision systems with larger Z/A ratios and significant scale differences, these factors will also influence the acceptance and rejection of baryon junction signals. In the future, further evidence supporting the baryon junction hypothesis will be sought in O+O and Au+Au at √sNN = 200 GeV.

Speaker: Wendi Lv

25 Polarized dissociation and spin alignment of Moving heavy quarkonium in a quark-gluon-plasma

"Recent experiments have found spin alignment of $J/\psi$ with respect to event plane in heavy ion collisions, suggesting a medium effect that is spin dependent. We propose a possible mechanism with polarized dissociation from the motion of $J/\psi$ with respect to the medium.
We calculate polarized dissociation rate for quarkonium spin triplet state from spin chromomagnetic coupling in the potential non-relativistic QCD framework. This is done for the leading order gluo-dissociation process and next to leading order inelastic Coulomb scattering process. The polarized dissociation rate is expressed as a function of relative velocity between quarkonium and QGP and the quantization axis. Applying the polarized dissociation rate to quarkonium evolution with dissociation effect only in a Bjorken flow, we find the spin $0$ state to dissociate less than the other spin states, leading to positive $\rho_{00}-1/3$. Regeneration contribution is expected to give a contribution with the opposite sign."

Speaker: Zhishun Chen

26 Charmonium production in Ru+Ru and Zr+Zr collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV with STAR

"Charmonium is an important to probe the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions due to the modification of its yield by the effects of dissociation and regeneration in QGP. The production of $J/\psi$ in heavy ion collisions has been extensively studied at RHIC energies. However, many new observables studied at LHC energies are yet to be explored at RHIC energies. 4 billion isobaric collisions ($^{96}_{44}Ru$ + $^{96}_{44}Ru$ and $^{96}_{40}Zr$ + $^{96}_{40}Zr$) at $\sqrt{s_\mathrm{NN}}$ = 200 GeV has been collected by STAR in 2018, providing a unique opportunity for the study of charmonium with observables has never been explored at RHIC before.

In this contribution, the first measurement of $\psi(2\rm{S})$ production in heavy ion collisions at RHIC will be presented with the 4B isobaric collision date. The J/$\psi$ and $\psi(2\rm{S})$ signals are reconstructed via the $e^{+}e^{-}$ decay channel with machine learning technique. Centrality and transverse momentum dependence of the ratio of $\psi(2\rm{S})$ yield over that of J/$\psi$ will be shown and physics implication will be discussed."

Speaker: Yan Wang

27 Nuclear modification of B_c mesons in relativistic heavy-ion collisions based on a linear Boltzmann transport model

The nuclear modification factor ($R_\mathrm{AA}$) of $B_c$ mesons in high-energy nuclear collisions provides a novel probe of heavy quark interactions with the quark-gluon plasma (QGP) medium. Based on a linear Boltzmann transport model that incorporates both Yukawa and string types of interactions between heavy quarks and the QGP, we study the production and evolution of heavy quarks and $B_c$ mesons within the same framework. A $B_c$ bound state dissociates while one of its constituent heavy quarks scatters with the QGP with momentum transfer greater than its binding energy. The medium-modified charm and bottom quarks can recombine into $B_c$ mesons, and the medium-modified bottom quarks can also fragment to $B_c$ mesons. We find that most primordial $B_c$ mesons produced by the initial hard collisions dissociate inside the QGP. The $B_c$ production is dominated by recombination at low transverse momentum, while it is dominated by fragmentation at high transverse momentum. The string interaction dominates over the Yukawa interaction in the nuclear modification of $B_c$ mesons. The participant number dependence of the $B_c$ meson $R_\mathrm{AA}$ is determined by the complicated interplay between the heavy quark yield, energy loss, and the QGP volume. We obtain a reasonable description of the $R_\mathrm{AA}$ of $B_c$ mesons in Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$~TeV, and provide predictions for Au+Au collisions at $\sqrt{s_\mathrm{NN}}=200$~GeV.

Speaker: Lejing Zhang

15:25 Coffee

28 Machine learning

Speaker: LongGang Pang (Central China Normal University)

29 Gluon Mass Separation from Machine Learning

In this work, we have applied artificial neural networks to model the mass functions of chromo-electric and chromo-magnetic gluons separately within the quasi-particle framework. By using a dual residual network architecture with appropriate regularization, we were able to reproduce lattice QCD thermodynamic data with good accuracy.

Speaker: Jie Mei

30 Free discussion (Yi Yin etc.)

18:30 Dinner

Sunday 3 August

31 Imaging shapes of atomic nuclei across energy scales

Speaker: Chunjian Zhang (Fudan University)

32 Bayesian inference of nuclear incompressibility from collective flow in mid-central Au+Au collisions

The incompressibility K of symmetric nuclear matter is determined using a Bayesian analysis of collective flow data in mid-central Au+Au collisions at 400 MeV/nucleon using a Gaussian process (GP) emulator of the isospin-dependent quantum molecular dynamics (IQMD) model for heavy-ion collisions, considering scenarios with and without the momentum dependence of single-nucleon potentials. The purposes of this work are threefold. Firstly, we infer the K by Bayesian inference, with or without considering the the momentum dependence of single-nucleon potentials. Secondly, we investigate how the inference of K may depend on the observables used. Thirdly, we investigate the energy dependence of the incompressibility K at 400-1500 MeV/nucleon using observables rapidity and transverse momentum dependence of proton elliptic flow.

Speaker: Jinmei Wang

10:20 Coffee

33 Energy loss of heavy flavor quarks in color string medium

"In this talk, we present our preliminary results on the estimation of the energy loss of heavy flavor (HF) quarks in the quark-gluon string medium in minimum bias p+p collisions at LHC energies.

This study is inspired by the ongoing hot debates on whether tiny droplets of liquid Quark-Gluon Plasma (QGP) can be formed in small colliding systems [1,2]. A number of observations indeed supports this assumption in high-multiplicity p+p at LHC, e.g. measured charged hadron azimuthal anisotropies [3] and strangeness enhancement [4]. On the other hand, there exist some natural limitations of hydrodynamical interpretation [5,6].

In this work, we assume that system in a p+p collision can be represented by overlapping quark-gluon strings originated from multi-pomeron exchanges [7,8]. On the one hand, this picture can be considered as the pre-equilibrium stage of the system evolution in relativistic hadron or heavy ion collisions. It can be followed by expanding QGP in local thermal equilibrium to which color strings act as sources [9]. On the other hand, QGP may never be formed in an event and, then, the quark-gluon strings would directly fragment into observed hadrons [10,11].

In this report, we focus on the estimation of the magnitude of transverse momentum loss of charm and bottom quarks, produced in initial hard scattering and propagating through quark-gluon soft strings formed. String overlaps result in the fluctuations of the energy density of the color field [12] whose influence is manifested and studied via elastic collisions of HF quarks with gluons in color strings. The simulation is performed event-by-event with fluctuating number of strings as well as their longitudinal oscillations [13], which creates dynamically initialized medium each time step.

The result is compared with the corresponding HF quarks’ energy losses in expanding hydro scenario in EPOS4HQ [14] and in static glasma fields of Color-Glass Condensate (CGC) approach [15].

[1] R. D. Weller, P. Romatschke, Phys. Lett. B 774, 351-356 (2017).
[2] Y. Zhou et al., Nucl. Phys. A 1005, 121908 (2021).
[3] V. Khachatryan et al. [CMS Collaboration], JHEP 09, 091 (2010).
[4] J. Adam et al. [ALICE Collaboration], Nature Phys. 13, 535-539 (2017).
[5] P. Romatschke, Phys. Rev. Lett. 120 (2018) 012301.
[6] V. E. Ambrus, S. Schlichting, C. Werthmann, Phys. Rev. Lett. 130, 15, 152301 (2023).
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Speaker: Daria Prokhorova

34 Performance study of Omega_c production in proton-proton collisions at 13.6 TeV with ALICE

"Heavy quarks are excellent probes for studying the quark-gluon plasma (QGP produced in the initial hard-scattering traverse the full space–time evolution of the QGP. Measurements of heavy-flavour hadron production in proton–proton collisions provide a baseline for heavy-ion collision research and a test of perturbative Quantum Chromodynamics (QCD). The first measurements of $\Omega_{c}^{0}$ in pp collisions during ALICE Run 2 showed an enhancement of the $\Omega_{c}^{0} / \mathrm{D} ^{0}$ baryon-to-meson ratio, which is similar to other charm baryon-to-meson ratios observed. However, the large uncertainties of $\Omega_{c}^{0}$ measurements limit the conclusions.
In this contribution, the performance of the $\Omega_{c}^{0}$ production in pp collisions at $\sqrt{S} = 13.6 $ TeV with ALICE Run 3 is shown. The measurements are compared to the Run 2 published results."

Speaker: Yunfan Liu

35 Measurement of prompt and non-prompt Lambda_c baryons elliptic flow in PbPb collisions at 5.36 TeV in 30--50% centrality class

"Heavy quarks (charm and beauty) are useful probes for investigating the properties of the quark-gluon plasma (QGP) generated in ultra-relativistic heavy-ion collisions. Their participation in the collective motion of the medium can be assessed by measuring the charm-hadron elliptic-flow coefficient , originating from the initial-state spatial asymmetry in non-central heavy-ion collisions. These measurements provide fundamental inputs to constrain theoretical models describing the charm-quark transport in the QGP, as well as its possible thermalization in the medium. In addition, the comparison between meson and baryon can provide further insights into medium-induced phenomena, such as the radial flow and the charm-quark hadronization via coalescence.
In this contribution, the first measurements of charm baryon $\Lambda_c$ in 30-50% centrality intervals of Pb–Pb collisions at $\sqrt{s_{NN}}$= 5.36 TeV collected by the ALICE experiment during the LHC Run 3 are shown. The measurements are compared to model predictions that incorporate various implementations of heavy-quark interaction and hadronization with the QGP constituents."

Speaker: Xufei Xue

36 Investigation of $T_{cs0}^{*}(2870)^{0}$ in pp collisions at 7 TeV with the PACIAE model

We have used the parton and hadron cascade model PACIAE together with the Dynamically Constrained Phase-space Coalescence model (DCPC) to study the $T_{cs0}^{*}(2870)^{0}$ production in $pp$ collision at $\sqrt{s}$ = 7 TeV, in line with the LHCb observation of $T_{cs0}^{*}(2870)^{0}$ in the $B^{-}\to D^{-}D^{0}K^{0}_{S}$ decays in $pp$ collisions at $\sqrt{s}$ = 7, 8, and 13 TeV [PRL 134(2025)101901]. The final hadronic states of the $pp$ collisions at $\sqrt{s}$ = 7 TeV are first simulated by the PACIAE model. Three
sets of $T_{cs0}^{*}(2870)^{0}$ candidates are then recombined by the DCPC model using the constituent meson pair of $D^{0}K^{0}_{S}$, $D^{+}K^{-}$, and $D^{-}K^{+}$ based on the above simulated final hadronic states, respectively. We calculate their rapidity distributions, transverse momentum spectra, and angular distribution between the two component mesons, as well as angular distribution between $D$ component meson and $T_{cs0}^{*}(2870)^{0}$. Our results show that the yields of three $T_{cs0}^{*}(2870)^{0}$ candidates follow the magnitude order of $D^{+}K^{-}$ $>$ $D^{-}K^{+}$ $\sim$ $D^{0}K^{0}_{S}$ (the latter two are nearly equal indeed). Similar ordering behavior is also observed in the aforementioned distributions.

Speaker: Qiang Wang

12:20 Lunch

37 PRad-Ⅱ Experiment - A High-Precision Measurement of Proton Charge Radius at Jefferson Lab

Accurate proton charge radius is essential for high-precision QED calculations of atomic energy levels, and to test the Standard Model. It also has a strong impact on the Rydberg constant. Typically, one can measure the proton charge radius using ordinary hydrogen spectroscopy or elastic e-p scattering. However, in 2010, the first muonic hydrogen spectroscopy experiment, with an unprecedented precision (0.1%), yielded a radius result that was 7σ smaller than previous measurements. This unexpected discrepancy is often referred to as the “proton charge radius puzzle”. In the past decade, significant progress has been made in both theory and experiment, yet many problems remain. For example, the $G_E^p$ form factor results are inconsistent between PRad and Mainz experiments. In this talk, I will introduce the PRad measurement, and also its upgraded experiment PRad-Ⅱ which will run at early 2026, aiming a factor of 3 smaller total uncertainty compared to PRad. This new experiment will help address discrepancies of different scattering measurements.

Speaker: Yuan Li

38 Meson Structure Program at EicC

"As the simplest quark-antiquark systems, pions and kaons are pseudo Nambu-Goldstone bosons closely related to the spontaneous symmetry breaking of the strong interaction. The study of their form factors and parton distribution functions is not only key to understanding their internal structures, but also tied to the mechanism of Emergent Hadron Mass, one of the mass generation mechanisms in the Standard Model, together with Higgs boson mechanism. Despite the long-standing discovery of pions and kaons, there is still a lack of understanding of their internal structure and dynamic characteristics, especially given the scarcity of experimental data due to their instability. However, the Sullivan process, taking advantage of the virtual meson cloud of a nucleon, provides a special approach to overcome this difficulty. Such an approach has been validated at HERA, DESY, JLab, and will be adopted by future EIC and EicC to collect more data in a wider kinematic range.
In this talk, I will discuss in detail how EicC can provide a unique platform for studying the structure of pions and kaons, and present their projected results. I will also emphasize the uniqueness of the EicC, and its complementarity to other facilities, such as JLab and EIC."

Speaker: Zongyang Lu

39 Measurement of charged jet v2 in Pb-Pb collisions at 5.36 TeV with ALICE

A jet is a spray of collimated hadrons originating from the fragmentation of an energetic parton. In heavy-ion collisions, jets traverse the colored medium and lose energy via induced gluon radiation and elastic scattering, which modify jet yields and structure. When the overlap of the colliding nuclei is small, the transverse profile of the quark-gluon plasma (QGP) is expected to become more elliptical in shape. This geometrical shape results in different QGP path lengths for partons emitted at different angles, resulting in an azimuthal anisotropy of the energy loss. This anisotropy alters the pT differential yield of jets and is quantified by the second-order flow coefficient, v2, of the jets. Therefore, measurements of jet v2 are expected to be sensitive to QGP properties and to the path length dependence of energy loss. Based on the high statistics data samples collected during Run 3, using ALICE upgraded detectors, we present the first analysis of inclusive charged-particle jet v2 in Pb-Pb collisions at \sqrt{s_{\rm NN}} = 5.36 TeV. The low pT reach of this measurement, which is unique to ALICE, is especially important in constraining theoretical models and elucidating the mechanisms which generate jet v2. The results will be also compared to existing jet v2 measurements.

Speaker: Yubiao Wang

40 Investigating system size dependence of strange hadron production at 200 GeV at STAR

"There are significant discussions in the field about the initial conditions, including the size of the system, needed to generate a quark-gluon plasma (QGP). Strangeness production serves as a sensitive probe into the properties of the QGP. It is expected that the Ω/𝜙 ratios in different colliding systems may reveal the minimum colliding system size required to produce QGP.
In this poster, we will present the transverse-momentum ($𝑝_T$) spectra of strange hadron (𝜙, Ω, anti-Ω) in isobar (Ru+Ru and Zr+Zr) and O+O collisions at sqrt(𝑠_NN) = 200 GeV at mid-rapidity (y < |0.5|) and the Ω/𝜙 ratios in those colliding systems. For O+O, the results with min-bias and high-multiplicity triggers will be shown separately. The O+O system has the extended kinematic coverage benefit from the iTPC upgrade, which extended the rapidity coverage and enhanced the particle identification capability compared with previous results."

Speaker: Xiongxiong Xu

14:55 Coffee

41 Acoustic thermalization towards spin, structure and collectivity

Speaker: Zhenyu Chen (Shandong University (CN))

18:30 Banquet