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53rd International Symposium on Multiparticle Dynamics (ISMD 2025)
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Mon Repos
Mon Repos
Corfu, Greece
George Zoupanos
(National Technical Univ. of Athens (GR)),
Kostas Kordas
(Aristotle University of Thessaloniki (GR)),
Jan Henryk Kalinowski
(University of Warsaw (PL)),
Stefan Kluth
(Max Planck Society (DE)),
Georg Wolschin
Description
53rd International Symposium on Multiparticle Dynamics (ISMD 2025), Corfu, Greece
(Foto CCBY3.0 Marc Ryckaert)
Welcome to the 53rd edition of the International Symposium on Multiparticle Dynamics (ISMD) series, bringing together physicists from across particle, nuclear, and astrophysics for talks and discussions on all aspects and consequences of the strong nuclear force and complex final states.
The ISMD 2025 meeting is hosted by the European Institute for Sciences and Their Applications (EISA).
All scientific sessions at ISMD are plenary to encourage cross-talk between areas and are organised into the following scientific tracks:
- Forward and diffractive physics
- Collectivity in high energy collisions: jets, flows, and other mechanisms
- QCD evolution of dense media and minimum-bias jets
- Hadronic final states in high pT interactions
- Hadron structure: pdfs, small-x and large-x physics
- Hadron spectroscopy
- Hadronic issues in heavy-flavor physics
- Astroparticle physics and cosmology
as well as a poster session with prize and associated short talks.
Location: Mon Repos Palace, Corfu
Begins 21 Sept 2025 (arrival day), ends 28 Sept 2025 (departure day)
Participants
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Opening: Registration
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Opening: Registration, welcomeConveners: George Zoupanos (National Technical Univ. of Athens (GR)), Stefan Kluth (Max Planck Society (DE))
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QCD evolution of dense media and minimum-bias jets: (3)
QCD evolution of dense media and minimum-bias jets
Convener: Sorina Popescu (Universität Münster (DE))-
1
Anomalous soft photons: Status and perspectives
We provide an overview of the soft-photon puzzle, i.e., of the long-standing discrepancy between experimental data and predictions based on Low's soft-photon theorem, also referred to as "anomalous" soft photon production, and we review the current theoretical understanding of soft radiation and soft theorems. We discuss how both topics can be addressed with the planned ALICE 3 detector at the LHC. The talk will be based on arXiv:2406.17959.
Speaker: Klaus Reygers (Heidelberg University (DE)) -
2
Gluon dominance model and multiparticle production
The gluon dominance model is developed to describe multiparticle production of secondary particles at high energies in lepton and hadron interactions, including annihilation processes and heavy quarkonium decays. According to this model, the multiparticle process is divided into two stages. The first stage describes the development of a quark-gluon cascade as a Markov branching process in the region of perturbation QCD. For the second stage, the transformation of quarks and gluons into observable hadrons (hadronization), a phenomenological scheme is proposed. It is universal and based on an experiment. The gluon dominance model demonstrates good agreement with data over a wide energy region.
It testifies that in hadron interactions valence quarks remain in the leading particles, and gluons are the sources of secondary hadrons. Quantitative estimates of the model parameters confirm the fragmentation mechanism of hadronization in leptonic interactions and the recombination mechanism in hadronic ones. The model description of the experimental distributions on the number of neutral pions in proton interactions at 50 GeV beams (the experiment at U-70, Protvino) in the high multiplicity region are presented for the first time. It is shown that the main contribution to this region is made by gluon fission. These results are useful for the development of Monte Carlo generators.Speaker: Prof. Elena Kokoulina -
3
Physics performance studies with the MPD experiment
The Multi-Purpose Detector (MPD) is the dedicated heavy-ion experiment of the Nuclotron-based Ion Collider fAcility (NICA), at the Joint Institute for Nuclear Research (JINR). It will operate in the energy range of 4 GeV$\le \sqrt{s_{NN}} \le$ 11 GeV and will search for novel phenomena in the baryon-rich region of the QCD phase diagram. A primary objective of the MPD experiment is the search for the Critical End Point and the predicted
first-order phase transition, which could be key to understanding the nature of strongly interacting matter under extreme conditions. The MPD experiment features a rich physics program that includes measurements of light hadron and (hyper)nuclei production, particle collective flow, correlations and fluctuations, the dielectron continuum, and in-medium modifications of vector meson properties in dense matter. This presentation will showcase selected results from physics feasibility studies for the MPD experiment based on simulated Bi+Bi collisions at \sqrt{s_{NN}}=9.2 GeV.Speaker: Jovan Milosevic (Vinca Institute of Nuclear Sciences (VINCA))
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1
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Astroparticle physics and cosmology
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4
Implications of $|U_{\mu i}| = |U_{\tau i}|$ in the Canonical Seesaw Mechanism and Associated Flavor Invariants
In the PMNS matrix, the relation $|U_{\mu i}| = |U_{\tau i}|$ (with $i = 1, 2, 3$) is currently favored by experimental data. This observation has sparked significant interest in the neutrino community due to its potential link to an underlying flavor symmetry. In this paper, we explore the implications of the condition $|U_{\mu i}| = |U_{\tau i}|$ within the framework of the canonical seesaw mechanism. While the minimal $\mu$-$\tau$ symmetry proposed in JHEP 06 (2022) 034 can explain this relation, we show that it is a sufficient but not necessary condition. In particular, we identify several other nontrivial scenarios that can also accommodate the observed PMNS matrix relation. Furthermore, we demonstrate that these scenarios are physically inequivalent, as evidenced by their distinct flavor invariants.
Speaker: Jianlong Lu (National University of Singapore)
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4
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10:40
Coffee / Tea break
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QCD evolution of dense media and minimum-bias jets: (4)
QCD evolution of dense media and minimum-bias jets
Convener: Sorina Popescu (Universität Münster (DE))-
5
Recent theory developments in the modelling of quarkonium production in URHIC collisions
In our contribution, we will present recent theoretical developments designed to improve the modelling of quarkonia formation in ultrarelativistic heavy ions collisions as well as the systematic uncertainty resulting the semiclassical treatment which is often used in such situation. Accurate modeling and understanding of quarkonium production in such case requires a formalism that preserves the quantum properties of a microscopic $Q\bar{Q}$ system while treating the interaction of such pairs with the QGP. The open quantum system approach has recently emerged as one of the most fruitful schemes to meet such requirements. However, the quantum master equations obtained so far in this approach and currently used to make predictions for the upsilon suppression at RHIC and LHC are derived assuming a strict ordering between the QGP temperature and the energy gaps ($\Delta E$) of the upsilon bound states. This limits their predictive power as the QGP cooling interpolates between the quantum Brownian regime ($T>\Delta E$) and the quantum optical regime ($T<\Delta E$)
In our contribution, we derive and present a more general non-abelian quantum master equation of the Linblad type, which does not suffer from these limitations and thus allows to faithfully describe the quantum evolution of the $Q\bar{Q}$ pairs during the whole QGP evolution. Preliminary results will be shown showing the interpolating features of our equation between the two regimes. We also establish the contact with the QME previously obtained in the QBM and QO regimes and give some concrete perspectives for its efficient solution.
When dealing with charmonia production in URHIC, a full quantum treatment is out of reach due to the numerous ccbar pairs produced. Semiclassical approximation have been recently been derived in [1] and used f.i.in [2]. Obtaining an estimate of the systematic error attached to this approximation is of crucial importance to assess the agreement with experimental data. In the second part of the talk, we investigate the accuracy of the SC approximation by benchmarking the corresponding evolutions on the exact solutions derived with the QME for the case of a single c-cbar pair [3].
refs:- J.-P. Blaizot and M.A. Escobedo, JHEP06(2018)034
- D.Y. Arrebato Villar et al., Phys.Rev.C 107 (2023) 5, 054913
- A. Daddi et al, https://arxiv.org/abs/2501.08772
Speaker: Pol-Bernard GOSSIAUX -
6
Percolation and de-confinement in relativistic nuclear collisions
Possible phase transition of strongly interacting matter from
hadron to a Quark Gluon Plasma (QGP) state have in the past considerable
interest. The clustering of color sources provides a framework of the partonic interactions in the initial stage of the collisions. The onset of de-confinement transition is identified by the spanning percolation cluster in 2D percolation.
The thermodynamical quantities, the initial temperature, and energy density derived from LHC data and Color String Percolation Model (CSPM) are used to obtain
degree of freedom in high multiplicity ${\it pp}$ collisions at
$\sqrt s = $ 5.02 and 13 TeV and Pb-Pb at $\sqrt {s_{NN}} =$ 2.76 and 5.02 TeV along with Xe-Xe at $\sqrt {s_{NN}} = $ 5.44 TeV.Speaker: Brijesh Kumar Srivastava (Purdue University (US)) -
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A color-tracking transport model for hadron and jet suppression in high-energy nuclear collisions
Jet serves as a crucial probe of the Quark-Gluon Plasma (QGP) created in relativistic heavy-ion collisions. While significant efforts have been devoted to developing transport models of jet interactions with the QGP, a simultaneous description of hadron and jet suppression within a unified framework still remains a great challenge. Based on our Linear Boltzmann Transport (LBT) model, we develop a transport approach that tracks the color information of partons during their elastic and inelastic scatterings with the QGP for the first time. This allows us to pause the Pythia vacuum shower of energetic partons at the thermal scale of the QGP, switch to parton transport inside the QGP, and in the end return to Pythia vacuum shower and hadronization outside the color-deconfined medium. Within this new framework, we are able to simultaneously describe the nuclear modification of different species of hadrons and jets, including inclusive and heavy flavor hadrons, as well as inclusive, charged, and heavy flavor jets. Our study highlights the essential role of scales in parton interactions with the QGP, and constructs a consistent picture of jet and hadron suppression in high-energy nuclear collisions.
Speaker: Yichao Dang (Shandong University) -
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Space-time geometry of small and large collision systems
Jet suppression has long been considered a signal for QGP formation in A-A nuclear collisions. Conventional approaches include a classical Glauber model to estimated number of nucleon participants Npart and N-N binary collisions Nbin. A spectrum ratio RAA incorporating Nbin and assuming hard-component (jet-related hadrons) factorization is intended to measure the extent of high-pt jet suppression in A-A relative to p-p. The same approach applied to smaller collision systems (p-Pb) returns nontrivial but ambiguous results. Detailed analysis of p-Pb spectra reveals that classical Glauber Monte Carlos substantially overestimate Npart and Nbin. An alternative method based on ensemble-mean pt data is compatible with spectrum data. Several spectrum features call into question assumed hard-component (jet) factorization implicit in the RAA definition and reveal the importance of "exclusivity" (a projectile nucleon can only interact with one target nucleon at a time) and relativistic time dilation. An updated version of a two-component spectrum model (TCM) isolates complete spectrum hard components (jet fragments) down to low hadron pt without assuming factorization. Revised TCM analysis provides surprising new results and places p-Pb and Pb-Pb systems within a common descriptive context.
Speaker: Thomas Trainor
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5
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12:50
Lunch break
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Collectivity in high energy collisions: jets, flows, and other mechanisms: (4)Conveners: Austin Alan Baty (University of Illinois Chicago), Yuuka Kanakubo (RIKEN iTHEMS / Lawrence Berkeley National Laboratory / UC Berkeley)
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9
Probing QCD collectivity at the smallest scale through high multiplicity jets in pp collisions at CMS
Recent CMS data revealed intriguing long-range correlations within high-multiplicity jets produced in proton-proton collisions, suggesting the potential onset of collective behavior, typically associated with heavy-ion collisions, at much smaller scales. Two-particle correlations in the “jet frame†show a surprising rise in elliptic flow harmonics, $v_{2}^*$, at large pseudorapidity separations (|$\eta$|> 2), in jets with high charged-particle multiplicities, a trend not reproduced by event generators like Pythia and Sherpa. In this talk, we present new measurements on the long-range near-side correlations in the jet frame, along with the transverse momentum and $j_{T}^*$ dependence of elliptic and triangular flow, across a wide range of jet multiplicity and transverse momentum. We further explore the role of jet substructure in driving the observed long-range azimuthal correlations. By selecting jets exhibiting prominent two-prong structures and comparing the results with models incorporating final-state rescatterings, we investigate the potential connection to the geometry of the initial-state jet system. These results offer fresh insights into collective effects at the smallest scales, potentially reshaping our understanding of QCD dynamics in its nonperturbative regime.
Speaker: Xiaoyu Liu (Rice University (US)) -
10
Modelling heavy-ion collisions at RHIC BES energies with fluid dynamics
In this talk, I discuss challenges in modelling collective expansion of baryon-rich medium in heavy-ion collisions at RHIC Beam Energy Scan or FAIR energies. Then I focus on specific approaches of multi-fluid dynamics and single-fluid dynamics with dynamical fluidization. I show generic conclusions from fluid-dynamic modelling at such energies, then present results from the two approaches and discuss strategies to improve them and to provide constraints on the properties of the underlying medium.
Speaker: Dr Iurii Karpenko (FNSPE CTU in Prague) -
11
Imprint of light and heavy nuclear structures in relativistic ion collisions
The study of nuclear structure has long been a fundamental aspect of nuclear physics, offering critical insights into the forces and interactions that govern matter at the subatomic level. Investigating nuclear structure in relation to complex nucleon-nucleon interactions poses significant challenges in low-energy nuclear physics, prompting extensive research into various phenomenological models and experimental approaches. In contemporary nuclear physics, relativistic nuclear collisions at facilities such as RHIC and LHC have emerged as particularly effective methodologies, enabling a comprehensive analysis of the structural properties associated with colliding nuclei.
In this context, I present my recent research on the influence of $\alpha$ cluster structures in relativistic light nuclear collisions and their connection to flow fluctuations in ultra-relativistic ion collisions. Utilizing a cluster framework, I analyze the nucleonic configurations for $^{16}$O and $^{20}$Ne as predicted by various \textit{ab initio} models. My focus is on how cluster parameters impact two-point correlators, employing a rotor model for both symmetric (O+O and Ne+Ne) and asymmetric (Pb+O and Pb+Ne) collisions. Additionally, I demonstrate that understanding nucleon-nucleon interactions is essential for elucidating light nuclear structures, as these correlations are intricately encoded within the nucleon configurations. Furthermore, I reveal that the signatures of nuclear structures can be observed in identified particles. Our findings indicate a notable shift in the crossing points of observable ratios, specifically $\pi^{\pm} /p(\bar{p})$ and $\pi^{\pm}/K^{\pm}$. This novel observable shows that the crossing point occurs at higher $p_T$ values for quadrupole-deformed nuclei, as well as elevated ratio values associated with triaxiality in U+U and Au+Au collisions.
Speaker: Hadi Mehrabpour (Peking Univresity) -
12
Hot QCD matter probed via measurements of the speed of sound with CMS
A hot and dense quark–gluon medium is observed to be created in ultrarelativistic nuclear collisions, exhibiting striking collective flow behavior, with fluid-like properties well described by relativistic hydrodynamics, with minimal viscous dissipation. The characteristics of this medium are under intense investigation, and in particular, its thermodynamical properties. In this context, the measurement of the speed of sound provides a key probe, as it reflects the medium pressure response to variations in energy density. This observable has been investigated by studying the correlations between the average transverse momentum, p_T, and the event multiplicity of charged particles, N_{ch}, produced in head-on PbPb collisions at sqrt{s_{NN}} = 5.02 TeV, using data with integrated luminosity of 0.607 nb^{-1}, obtained by the CMS experiment at the CERN LHC. The resulting values for the speed of sound and temperature are the most precise to date. They are consistent with lattice QCD predictions and provide direct evidence for the formation of a deconfined, strongly interacting matter in such extreme conditions. More recently, CMS has extended the measurement of the speed of sound to pPb collisions, using data corresponding to integrated luminosities of 186.0 nb^{-1} at sqrt{s_{NN}} = 8.16 TeV and 0.509 nb^{-1} at sqrt{s_{NN}} = 5.02 TeV. The extracted values are found to be consistent with lattice QCD predictions within uncertainties and are also compared with theoretical models.This investigation is motivated by previous LHC observations of multiparticle correlations in small colliding systems (pp and pPb), which revealed collective behavior reminiscent of that seen in heavy-ion collisions. This talk presents the assembled results for PbPb and pPb collisions in this broader context.
Speaker: Sandra Padula (UNESP - Universidade Estadual Paulista (BR))
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9
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17:00
Coffee / Tea break
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Collectivity in high energy collisions: jets, flows, and other mechanisms: (4)Conveners: Yuuka Kanakubo (RIKEN iTHEMS / Lawrence Berkeley National Laboratory / UC Berkeley), Austin Alan Baty (University of Illinois Chicago)
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13
Two- and three-particle femtoscopy in small collision systems at LHCb
The new results on three-pion Bose-Einstein correlations measured with the sample of proton-proton collisions recorded at the centre-of-mass energy of √s = 7 TeV will be presented, being the first study of three-particle Bose-Einstein correlations measured in the forward region provided by the LHCb detector. The results are interpreted within the core-halo model for the first time in proton-proton collisions. Together with previous LHCb results on two-pion Bose–Einstein correlations measured for the first time in the forward rapidity region at LHC energies, it confirms the observation of collective phenomena in the small collision systems.
Speaker: Izabela Juszczak (Polish Academy of Sciences (PL)) -
14
Insights into the Baryon Correlation Puzzle via Angular Correlation Studies with ALICE
One of the most effective techniques for investigating the mechanism of baryon production is the study of angular correlations between two particles. Angular correlations represent a convolution of various physical processes, such as mini-jets, Bose-Einstein quantum statistics, conservation of momentum, resonances, and other phenomena that contribute to the unique behavior observed for different particle species.
Experimental results from proton-proton collisions at 7 TeV have revealed a pronounced anticorrelation — a phenomenon that has not been replicated by Monte Carlo models. This discovery triggered a series of studies that led to the formulation of what is now referred to as the “baryon correlation puzzle”.
In this work, the ALICE measurements of the angular correlation functions for identified particles (such as π±, K±, p–p̄, Λ–Λ̅ ) in pp, p–Pb, and Pb–Pb collisions at LHC energies of both Run 2 and Run 3 data across various multiplicity/centrality classes are presented. This new piece of the puzzle enhances the understanding of anticorrelation and raises new questions, prompting theorists to refine and expand existing theoretical models in search of new answers.
Speaker: Malgorzata Anna Janik (Warsaw University of Technology (PL)) -
15
Azimuth quadrupole pt spectra inferred from differential Pb-Pb PID v2(pt) data
Measure v2(pt) is interpreted to estimate the amplitude of an azimuth component of particle pt spectra arising from transverse (elliptic) flow of a dense QCD medium. Comparisons of v2 data with hydrodynamic (hydro) theory seem to indicate very low medium viscosity leading to attribution of a "perfect liquid." As defined v2(pt) is a ratio, with a single-particle spectrum appearing in its denominator. Its numerator represents a Fourier component -- an azimuth cylindrical quadrupole -- arising from a boosted (on transverse rapidity) particle source. The Cooper-Frye (CF) formalism may be used to describe emission from a boosted source based on relativistic kinematics. CF analysis reveals that the v2(pt) numerator includes pt in the transverse boost frame as a factor, which has major consequences for data interpretation. A unique quadrupole pt spectrum may be isolated from v2(pt) data and compared directly with the single-particle spectrum in the v2 denominator and with hydro theory. A monopole boost (aka radial flow) value may be estimated from v2(pt) data. Certain conjectured data trends such as meson vs baryon segregation and NCQ scaling may also be tested. Several novel results emerge via the Cooper-Frye analysis.
Speaker: Thomas Trainor -
16
Imprint of Light Nuclei Structure in Fixed-target Relativistic Nuclear Collisions
By smashing heavy nuclei at RHIC and the LHC and analysing the anisotropic expansion (flow) of the final state produced particles, unique information on the structure of the collided nuclei can be obtained. Existing efforts primarily focus on the colliding mode of heavy nuclei collisions. In contrast, nuclear structure studies with collisions of light nuclei and the fixed target mode have not been thoroughly explored despite their significant impact and broad interest.
This talk presents the results of two- and four-particle cumulants of anisotropic flow in the fixed-target $^{208}$Pb--$^{20}$Ne and $^{208}$Pb--$^{16}$O collisions at $\sqrt{s_{_\mathrm{NN}}}$ = 68.5 GeV, using the parton transport model AMPT. These results demonstrate a robust signature of nuclear structure effect that persists regardless of the complex dynamic evolution of the created systems. The comparison to the recent hydrodynamic calculations reveals a new possibility of uncovering the origins of collective flow in small systems. This study highlights the significant impact of the light nuclei collisions at the LHCb SMOG (SMOG2) project.Speaker: Zhiyong Lu (China Institute of Atomic Energy (CN))
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13
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19:30
Welcome recpetion: Choir, refreshments
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Collectivity in high energy collisions: jets, flows, and other mechanisms: (4)Conveners: Austin Alan Baty (University of Illinois Chicago), Yuuka Kanakubo (RIKEN iTHEMS / Lawrence Berkeley National Laboratory / UC Berkeley)
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17
Flow measurements at LHCb
Particle correlations are powerful tools for studying quantum chromodynamics in hadron collisions. In heavy-ion collisions, azimuthal angular correlations probe collective phenomena in hot, dense, nuclear media, such as QGP. In small collision systems, they could point to final-state effects or potential initial-state correlations. The LHCb experiment has the unique ability to study particle correlations in high-energy hadron collisions at forward rapidity, exploring a unique region with respect to other experiments, where longitudinal expansion becomes more important. In this contribution, recent results on collective flow from the LHCb experiment will be discussed.
Speaker: Samuel Belin (Universidade de Santiago de Compostela (ES)) -
18
sPHENIX Measurements of Bulk Properties and Collectivity at RHIC
sPHENIX is a next-generation collider detector at RHIC, featuring large-acceptance calorimeters and precision tracking systems. The detector was successfully commissioned and collected physics data in both p+p and Au+Au collisions in 2024. Full-scale Au+Au data taking is currently in progress in 2025.
sPHENIX has excellent capabilities for measuring bulk particle production—such as the charged-particle pseudorapidity density (dNch/dη) and transverse energy density (dET/dη), both of which will be published soon (arXiv:arXiv:2504.02240, arXiv:2504.02242).
It also has the ability to measure collective behavior in both large and small collision systems, supported by forward detectors including the sPHENIX Event Plane Detector (sEPD). These measurements provide important constraints on the initial-state conditions and bulk properties of collisions at RHIC energies.This talk presents measurements of dNch/dη, dET/dη, and azimuthal anisotropy coefficients in Au+Au collisions from sPHENIX. It also includes an overview of ongoing efforts to study collective behavior in small collision systems using the long-range two-particle correlation method.
Speaker: Yuko Sekiguchi (RIKEN) -
19
Thermal Radiation from an Analytic Hydrodynamic Model with Hadronic and QGP Sources in Heavy-Ion Collisions
In high-energy heavy-ion collisions, a nearly perfect fluid is formed, known as the strongly coupled quark-gluon plasma (QGP). After a short thermalization period, the evolution of this medium can be described by the equations of relativistic hydrodynamics. As the system expands and cools, the QGP undergoes a transition into hadronic matter, marking the onset of quark confinement. Direct photons offer insights into an essential stage of evolution, spanning from the onset of thermalization to the suppression of thermal photon production, which occurs within the hadronic phase. This paper builds upon and extends a previously published solution of relativistic hydrodynamics, incorporating an equation of state that falls within the same class as that predicted by lattice QCD. Based on this solution, a completely analytic model is constructed to describe thermal photon production, accounting for the quark-hadron transition. The model is tested against PHENIX measurements of non-prompt direct photon spectra in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. Good agreement is observed between the model predictions and the experimental data, enabling the investigation of the centrality dependence of the initial temperature. These results provide a benchmark for future theoretical and experimental studies of thermal radiation in heavy-ion collisions.
arXiv:2507.13240 [hep-ph]Speaker: Gábor Kasza -
20
Dynamical Effects in the Nuclear Modification Factor $R_{AA}
We present a detailed analysis of the nuclear modification factor $R_{AA}$ for charged particles produced in central Pb-Pb collisions at LHC energies, incorporating dynamical effects within a nonextensive framework. The study is based on a solution of the Plastino-Plastino Equation (PPE), a nonlinear Fokker-Planck-type equation that emerges naturally in the context of Tsallis nonextensive statistics and is particularly suited to describe systems with memory effects, long-range correlations, and intrinsic fluctuations---all of which are relevant in the quark-gluon plasma (QGP) formed in ultrarelativistic heavy-ion collisions.
To account for collective flow and the thermalised medium expansion, we embed the PPE dynamics into a Blast Wave model, allowing us to combine microscopic stochastic effects with macroscopic hydrodynamic expansion. The drag coefficient is assumed to follow a $q$-exponential dependence on momentum, representing a nontrivial coupling between the propagating partons and the evolving medium. Diffusion effects are found to be negligible in the transverse momentum range of interest, which justifies the focus on drift-dominated dynamics.
The resulting expression for $R_{AA}$, derived analytically and then confronted with experimental data at $\sqrt{s_{NN}} = 2.76$ and $5.02$ TeV, shows fair agreement with measurements. In particular, the observed oscillatory behaviour and suppression pattern are naturally reproduced without the need for ad hoc parametrisations. The combined use of the PPE and the Blast Wave model thus offers a consistent description of parton energy loss that incorporates both microscopic and collective aspects of the QGP.
These results suggest that dynamical corrections, when properly modelled, can significantly enhance our understanding of energy loss mechanisms and open a path toward a unified description of nuclear modification observables within a generalised non-equilibrium framework.
Speaker: Airton Deppman (Universidade de São Paulo)
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17
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10:40
Coffee / Tea break
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Collectivity in high energy collisions: jets, flows, and other mechanisms: (1)Conveners: Yuuka Kanakubo (RIKEN iTHEMS / Lawrence Berkeley National Laboratory / UC Berkeley), Austin Alan Baty (University of Illinois Chicago)
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21
Asymmetric muon-antimuon emission from Z0 decays: a clear magnetometer in relativistic heavy-ion collisions
An utterly intense magnetic field is expected to be generated in non-central heavy-ion collisions. Despite intense effort during the last few years, a clear signal of this field has not yet been found.
We show that a very clear signal of the presence of a strong magnetic field during the early stage of a high-energy heavy-ion collision is provided by the decay of the 𝑍0 into dimuon pairs. We find that the process is highly anisotropic, producing pairs mainly out of plane, as signaled by a negative value of 𝑣2, and leads to an antimuon transverse momentum distribution which peaks at a higher value of the transverse momentum compared to the peak of the muon transverse momentum distribution. The signal can be identified by comparing the dimuon-invariant mass and the individual muon and antimuon spectra produced in semicentral heavy-ion collisions with the corresponding scaled spectra produced in p+p collisions at the 𝑍0 peak.Speaker: Ana Mizher (UNICID)
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21
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QCD evolution of dense media and minimum-bias jets: (1)
QCD evolution of dense media and minimum-bias jets
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22
Turbulent Energy Flow as a Mechanism for Jet Quenching
Jets — collimated sprays of particles from high-energy quarks and gluons— lose energy when traversing the quark--gluon plasma, a phenomenon known as \emph{jet quenching}. We develop an analytic framework that captures this process through a turbulent gluon cascade, driven by medium-induced splittings at all angles. A non-linear rate equation, amplified by the medium length $L$, connects to a DGLAP-like evolution for the early collinear cascade above the medium resolution scale $\theta_c$. At high energies, the cascade exhibits an exponential energy-loss pattern, generalizing the classic Poisson model, and enabling resummation of leading $\alpha_s$ logarithms and $\alpha_s L$ effects. This approach also yields analytic insight into the strong-quenching regime, guiding future simulations.
Speaker: Dr Yacine Mehtar-Tani (Brookhaven National Laboratory)
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22
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Hadronic issues in heavy-flavour physics: (2)Conveners: Wolfgang Schaefer, Cristina Terrevoli (Universita e INFN, Bari (IT))
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23
Highlights of recent heavy-flavour hadron measurements
Heavy-flavor hadrons, containing charm or bottom quarks, serve as sensitive probes of perturbative QCD across a wide range of energy scales and collision systems. Recent experimental advances have significantly deepened our understanding of heavy-flavor production mechanisms, hadronization dynamics, and interactions with nuclear matter. Notably, recent measurements in proton-proton (pp) collisions reveal baryon-to-meson ratios for charm hadrons that are substantially higher than those observed in $\mathrm{e^+e^-}$ collisions, challenging the validity of theoretical models based on factorization and the universality of fragmentation functions. This presentation reviews the latest heavy-flavor hadron production results in both pp and heavy-ion collisions, with a focus on observables that provide new insights into charm and beauty quark hadronization.
Speaker: Grazia Luparello (Universita e INFN Trieste (IT)) -
24
Highlights from exotic heavy-flavor states
Recent years have seen major progress in the study of exotic hadrons—particles that go beyond the traditional quark–antiquark or three-quark picture. This talk will present selected highlights from experiments at the LHC and other facilities worldwide, including new discoveries of tetraquark and pentaquark candidates, along with advances in understanding the properties of such states. Particular attention will be given to heavy-flavor systems, where narrower widths provide a cleaner environment to identify regularities and explore the underlying mechanisms of hadron formation in QCD. The broader implications for hadronic dynamics, threshold effects, and coupled-channel amplitude analyses will be discussed in the context of multiple ISMD topics.
Speaker: Prof. Mikhail Mikhasenko (Ruhr Univeristy Bochum)
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23
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12:50
Lunch break
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Hadronic issues in heavy-flavour physics: (4)Conveners: Wolfgang Schaefer, Cristina Terrevoli (Universita e INFN, Bari (IT))
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25
Heavy-Flavor Fragmentation from HF-NRevo: Status and Prospects
We report progress on the Heavy-Flavor Non-Relativistic Evolution (HF-NRevo) setup, a novel methodology to address the quarkonium formation within the fragmentation approximation. Our analysis addresses the moderate to large transverse-momentum regime, where the production mechanism based on the leading-twist collinear fragmentation from a single parton is expected to prevail over the higher-twist emission, directly from the hard-scattering subprocess, of the constituent heavy-quark pair. We rely upon Non-Relativistic-QCD (NRQCD) next-to-leading calculations for all the parton fragmentation channels to quarkonia, which we take as proxies for initial-scale inputs. Thus, a complete set of variable-flavor number-scheme fragmentation functions, named NRFF1.0, are built through standard DGLAP evolution. Statistical errors are assessed via a Monte Carlo, replica-like approach that also accounts for Missing Higher-Order Uncertainties (MHOUs). The link between the NRFF1.0 approach and the MCscales one will be discussed. As a prospect, the use of HF-NRevo to address the quarkonium-in-jet fragmentation will be highlighted
Speaker: Dr Francesco Giovanni Celiberto (UAH Madrid) -
26
Upsilon spectroscopy in the quark-gluon plasma
In relativistic heavy-ion collisions at RHIC and LHC energies, the spectroscopy of heavy-quarkonia states such as $J/\psi, \psi'$ and $\Upsilon(nS)$ that are mostly produced in the initial stages of the collision is modified through the presence of the hot plasma of gluons and light quarks. Here, we investigate the in-medium effects on the $\Upsilon$ and $\chi_b$ states in our theoretical Heidelberg model.
It considers, in particular, screening of the real quark-antiquark potential, collisional damping through the imaginary part of this potential, gluon-induced dissociation of the six states involved below threshold, and reduction of the feed-down contribution to the $\Upsilon(1S)$ spin-triplet ground state because of the screening of the higher-lying states [1]. Centrality- and transverse-momentum dependent results are compared with CMS and STAR data for the $\Upsilon(nS)$ states, including recent CMS results [2] for $\Upsilon(3S)$.
We also apply the model to $\Upsilon$ physics in p-Pb collisions, where the hot-medium effects can not be neglected, although cold-matter effects are dominant - as is shown in a detailed comparison with LHCb [3] and ALICE [4] data for $\sqrt{s_{NN}}=8.16$ TeV p-Pb.
[1] G. Wolschin, Int. J. Mod. Phys. A 35, 2030016 (2020).
[2] A. Tumasyan et al. (CMS Coll.), Phys. Rev. Lett. 133, 022302 (2024).
[3] R. Aaij et al. (LHCb Coll.), JHEP 11, 194 (2018).
[4] S. Acharya et al. (ALICE Coll.), Phys. Lett. B 806, 135486 (2020).Speaker: Georg Wolschin -
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Heavy flavor transport and production (online)
We present a comprehensive analysis of heavy-flavor transport and hadronization in ultra-relativistic heavy-ion collisions. An updated version of the Quasi-Particle Model (QPM), denoted QPM$_p$, is introduced byincluding momentum-dependent parton masses consistent with QCD asymptotic freedom. This extensionimproves the agreement with lattice QCD calculations of quark susceptibilities. Within an event-by-eventtransport framework based on Langevin dynamics, we compute the main heavy flavour observable likenuclear modification factor $R_{AA}(p_T)$ and the anisotropic flow coefficients $v_n(p_T)$ for $D$mesons, achieving good agreement with current experimental data. We emphasize the critical role ofmomentum-dependent interactions in reproducing key observables and ensuring consistency with recentlattice QCD results. Finally, we investigate the enhancement of heavy baryon production using ahadronization scheme that combines recombination and fragmentation. This model successfully reproducesthe $\Lambda_c/D^0$, $\Xi_c/D^0$, and $\Omega_c/D^0$ ratios across pp, pA, and AA systems.Predictions are also extended to multi-charmed and bottom baryons over a broad range of system sizes.
Speaker: Salvatore Plumari -
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Semileptonic heavy flavored $B$ meson decays in a QCD-inspired model (online)
In the realm of flavor changing processes can probe new physics (NP) at scales beyond the reach of current experiments, we analyze semileptonic decays of $B$, $B_s$ and $B_c$ mesons using \emph{Relativistic Independent Quark Model - a QCD inspired model} emphasizing the harmonic potential model-dependent analysis of heavy flavor dynamics. Our predicted branching fractions and physical observables such as $P_{\tau}(D_{(s)}^{(*)})$, $F_{L}(D_{(s)}^{(*)})$ in the $B$ decays show good agreement with the lattice and experimental measurements. In particular, our predictions for $P_{\tau}(D^{(*)})$ in $B_c$ decays offer valuable information in the absence of lattice data for this observable. We also provide a detailed study of form factors across the full kinematic range. While the lack of clear deviations in high energy collider data challenges the TeV - scale NP paradigm, semileptonic decays of heavy mesons always remain a powerful probe of NP, especially beyond the reach of direct searches. Therefore, while lattice QCD remains the gold standard for theoretical predictions, QCD-inspired models serve as valuable alternatives in regions where lattice results are unavailable.
Speaker: Ms Sonali Patnaik (National Institute of Science Education and Research)
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17:00
Coffee / Tea break
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Hadronic final states in high pT interactions: (4)Conveners: Chia-Ming Kuo (National Central University (TW)), Giancarlo Ferrera (University of Milan)
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"What have we learned about the minimal conditions for observing flow-like signals, from e+e- to AA collisions?"
Long-range multiparticle correlations as observed in the ultrarelativistic collisions of heavy ions at RHIC and the LHC has long been held as a signature of hydrodynamic flow in the novel phase of hot and dense matter known as the quark gluon plasma. However, these correlations, manifesting most simply as an elliptical Fourier coefficient or v$_{2}$, has subsequently been observed not just in collisions of heavy ions, but also in collisions of light ions, in collisions of protons with ions, in high-multiplicitiy proton-proton collisions, in ultra-peripheral heavy ion collisions, and even recently in analysis of archival data of high energy e+e- collisions from the ALEPH detector at LEP. In this talk the state of multiparticle correlation measurements across collision systems will be reviewed, with a particular focus on what we can and cannot conclude regarding the minimal conditions for flow-like signals, given current experimental limitations. Furthermore, the distinction between a flow-like signal and the underlying mechanism being true hydrodynamic flow will be explored, as the minimal conditions for observing each should be considered distinct. Finally, future prospects for measuring flow in small systems will be discussed.
Speaker: Christopher Mc Ginn (Massachusetts Inst. of Technology (US)) -
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Global extraction of proton Transverse Momentum Distributions
We discuss recent extractions of both unpolarized and polarized quark TMD Parton Distribution Functions (TMD PDFs) in the proton, as well as TMD Fragmentation Functions (TMD FFs). These results are based on global fits of Drell–Yan and Semi-Inclusive Deep-Inelastic Scattering (SIDIS) data sets performed by the MAP collaboration. We also compare our findings with those from other groups, highlighting similarities and differences in the extracted distributions.
Speaker: Mr Lorenzo Rossi (University of Milan & INFN) -
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Theoretical Uncertainties on the determination of the strong coupling from Z pT
I will analyse the theoretical uncertainties inherent in the determination of the strong coupling from the transverse momentum (pT) spectrum of the Z boson. Such analyses require fine control of percent-level theoretical effects in small pT region, not only in terms of their magnitude but also of their shape and that of the corresponding theoretical uncertainties. This is theoretically extremely challenging. In this talk I will analyse the associated theoretical uncertainties via the novel theoretical nuisance parameter approach. In particular, I will focus on the perturbative uncertainty from missing higher orders in resummation, and that associated with the parton distribution functions, as well as others if time allows.
Speaker: Thomas Cridge (DESY) -
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Renormalon effects to the transverse momentum sensitive observables
In this talk, I will present an analysis based on renormalon techniques in the large-beta0 limit to estimate leading non-perturbative power corrections relevant to collider observables. As a proof of concept, we apply this approach to e+e- collisions and successfully reproduce the leading non-perturbative corrections for observables sensitive to the invariant mass. Extending this framework, we present new results for observables sensitive to transverse momentum, which are complicated by rapidity divergences. Using the collinear anomaly formalism, we regulate these additional divergences and identify the leading renormalon contributions both in the anomaly exponent and in the remainder function. Furthermore, we examine the impact of the leading renormalon on the partonic cross section. Our results are complementary to resummation techniques and contribute toward a more complete hadronic description of collider observables.
Speaker: Dr Goutam Das (RWTH Aachen University)
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Hadron structure: pdfs, small-x and large-x physics: (4)Convener: Thomas Cridge (DESY)
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Partonic distributions from Lattice QCD
In this talk, we discuss the recent progress in Lattice QCD extractions of partonic distributions of the nucleon. The focus of the talk are parton distribution functions (PDFs) as well as generalized parton distributions (GPDs), at leading twist and at twist-3. We review theoretical and practical advances in this field and present a selection of results obtained in the last years. Finally, we also discuss prospects for synergy with phenomenology and experiment.
Speaker: Krzysztof Cichy -
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Small- and Large-x resummations in PDF fits
I will review the state-of-the-art determinations of parton distribution functions obtained with the inclusion of large-x and small-x logarithmic resummations in the theoretical predictions, and present future perspectives in this context.
Speaker: Marco Bonvini (INFN, Rome 1 Unit) -
35
Theory uncertainties from theory nuisance parameters in fixed-order QCD (online)
Precision computations for standard candle processes are a staple of the physics programme at colliders such as the Large Hadron Collider (LHC). The highest precision can be achieved in perturbative computations. In perturbation theory, however, calculations truncated at a fixed order inevitably have inherent theoretical uncertainty. This uncertainty quantifies the contributions from the missing higher-order terms (MHOU) that have not been accounted for. Traditionally, scale variation has been employed to estimate this uncertainty. In this talk, I discuss a prescription to directly incorporate these missing higher-order terms through theory nuisance parameters (TNPs). By varying these parameters, the associated uncertainty can effectively be estimated.
I will elaborate on how this methodology can be applied across various processes pertinent to LHC physics, specifically at next-to-leading (NLO) and next-to-next-to-leading order (NNLO) in perturbation theory. The findings reveal that in scenarios where scale variations yield consistent and reliable results, we can successfully mimic their outcomes using TNPs. Moreover, we will observe a considerable improvement in scenarios where traditional scale variation methods tend to underestimate the uncertainty involved. (Remote talk)
Speaker: Rene Poncelet (IFJ PAN Krakow) -
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On the origin of the peak of the sound velocity for isospin imbalanced strongly interacting matter
We study the properties of a system composed of strongly interacting matter with an isospin imbalance, using as an effective description of QCD the two-flavor Linear Sigma Model with quarks. From the one-loop effective
potential, including the two light quarks, pions and
sigma contributions, and enforcing the restrictions imposed by chiral symmetry, we show that the development of an isospin condensate comes together with the emergence of a Goldstone mode that provides a constraint for the chiral and isospin condensates as a result of a non-trivial mixing between the charged pions and the sigma. We compute the thermodynamical quantities of interest and in particular the sound velocity squared, showing that it presents a maximum for an isospin chemical potential similar to the one reported by lattice QCD results and also with a similar height. Therefore, we attribute the origin of the peak of the sound velocity to the proper treatment of the Goldstone mode and to the non-trivial mixing of the charged pions and sigma in the isospin condensed phase.Speaker: Prof. Alejandro Ayala (Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico)
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10:40
Coffee / Tea
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Hadron spectroscopy: (4)Convener: Zhiqing Liu
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37
observation of a family of all-charm tetraquark states
We present a comprehensive study of near-threshold structures in the J/\psi J/\psi mass spectrum using the fully reconstructed J/\psi J/\psi \rightarrow 4\mu final state, based on proton-proton collision data at \sqrt{s} = 13 and 13.6 TeV collected by the CMS experiment. With approximately four times more J/\psi pair candidates compared to the previous Run 2 dataset, the combined data sample enables a significantly enhanced sensitivity to rare structures. In the mass range between 6 and 8 GeV, three peaks are observed with significances well above 5σ, consistent with the previously reported tetraquark candidates X(6600), X(6900), and X(7100). Two pronounced dips, also exceeding 5σ in significance, are identified between the peaks, highlighting the presence of strong interference effects. A complementary search in the J/\psi \psi(2S) \rightarrow 4\mu final state reveals a consistent two-peak structure corresponding to the X(6900) and X(7100), with measured masses and widths compatible within uncertainties. To further investigate the nature of the observed states, a spin-parity analysis is performed using a matrix-element-based approach, testing multiple J^P hypotheses. The results favor a J^P = 2^+ assignment, offering new insights into the internal dynamics of these exotic resonances. This analysis, based on the Run 2 data, provides the most detailed picture to date of the fully-charm tetraquark landscape.
Speaker: Kai Yi (Nanjing Normal University (CN)) -
38
Conventional heavy flavor hadron spectroscopy at LHCb
The LHCb experiment is well suited to the spectroscopy of heavy flavor hadrons. The proton-proton collisions provided by the Large Hadron Collider produce a variety of heavy flavor states, and the excellent vertex and momentum resolution of the LHCb detector enables precision studies of hadron properties. Access to the kinematics of full decay chains allows amplitude analysis, which provides detailed information on the properties of intermediate resonances. This talk will present recent measurements in conventional heavy flavor hadron spectroscopy from LHCb, highlighting contributions to our understanding of the hadron spectrum.
Speaker: Dr Paras Naik (University of Liverpool (GB)) -
39
Light Hadron Spectroscopy at BESIII
Using the world’s largest samples of $J/\psi$ and $\psi(3686)$ events produced in e+e- annihilation, BESIII is uniquely positioned to study light hadrons in radiative and hadronic charmonium decays. In particular, exotic hadron candidates including multiquark states, hybrid mesons, and glueballs can be studied in high detail. Recent highlights on the light exotics searches and on baryon spectroscopy will be presented.
Speaker: Isabella Garzia -
40
Multi-hadron dynamics via lattice QCD
Multi-hadron reactions play a key role in several subfields of nuclear and particle physics, including hadron spectroscopy, nuclear reactions, and precision tests of the Standard Model of particle physics. Despite the non-perturbative nature of quantum chromodynamics (QCD), the advent of lattice QCD has enabled the direct constraint of various hadronic reactions from the Standard Model. In this talk, I review the challenges and successes encountered in studying these reactions using lattice QCD, highlighting recent results that shed light on multi-hadron dynamics. I conclude with a brief outlook on the future directions of this exciting field.
Speaker: Raul Briceno (UC Berkeley & LBNL)
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Hadronic final states in high pT interactions
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First results of spin program of new generation sPHENIX detector at RHIC
The sPHENIX experiment is a new experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It was constructed as an upgrade of the PHENIX experiment with the goal to complete the scientific mission of RHIC in studying the quark-gluon plasma and the spin structure of the nucleon. The sPHENIX detector will provide precision vertexing, tracking and electromagnetic and hadronic calorimetry in the central pseudorapidity region |η| < 1.1, with full azimuth coverage, at the full RHIC collision rate, delivering unprecedented data sets for hard probe tomography measurements at RHIC. The sPHENIX detector accumulated production data of transversely polarized proton+proton collisions at a center-of-mass energy of 200 GeV. The physics goals of the spin program and first preliminary results of will be presented.
Speaker: Dr itaru nakagawa
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42
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Hadron structure: pdfs, small-x and large-x physics: (3)
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Nuclear parton distribution functions
We review the theoretical foundations, methodological approaches and current status of the determination of nuclear parton distribution functions (PDFs). A large variety of measurements in fixed-target and collider experiments provide increasingly precise constraints on various aspects of nuclear PDFs, including shadowing, antishadowing, the EMC effect, Fermi motion, flavour separation, deuteron binding, target-mass and other higher-twist effects. We give particular emphasis to measurements carried out in proton-lead collisions at the Large Hadron Collider, which have revolutionised the global analysis during the past decade. These measurements include electroweak boson, isolated photon, single inclusive hadron, jet, and heavy-flavour observables.
Speaker: Michael Klasen -
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Theory and modelling of multi-parton distributions
I will discuss progress in the theoretical treatment and modelling of multi-parton distibutions, focussing on the inclusion of various types of correlations beyond the simple “pocket formula” approach. Such distributions are needed for theoretical predictions of multiple parton scattering cross sections at the LHC. I will focus mainly on the case of double parton distributions, but will also briefly discuss the case of triple parton distributons.
Speaker: Jonathan Richard Gaunt (The University of Manchester (GB)) -
45
Hadronization dynamics in e-A scattering at Jefferson Lab
Hadronization, the non-perturbative process through which quarks become color-neutral hadrons, remains a key challenge in QCD. Complementary insights into this process come from diverse experiments, including Drell-Yan, Heavy-Ion collisions, and Semi-Inclusive Deep-Inelastic Scattering (SIDIS).
This talk focuses on recent and ongoing SIDIS studies off nuclear targets, a program initiated by HERMES at DESY in 1990’s and now advanced with high-precision measurements with CLAS and CLAS12 at Jefferson Lab. Employing SIDIS’s ability to probe the time-dependence of hadronization by using nuclei of varying sizes, a series of measurements have been conducted with a 5.014 GeV electron beam on a double-target system (D plus C, Fe or Pb) in CLAS and recently extended with 11 GeV upgrade using CLAS12. I will review recent CLAS results and discuss future opportunities.
Speaker: Taisiya Mineeva (Universidad de La Serena)
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43
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10:40
Coffee / Tea break
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Hadron spectroscopy: (4)
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46
Centrality dependence of Lévy-stable two-pion Bose-Einstein correlations indicate a second QCD transition in sqrt(s(NN))= 200 GeV Au+Au collisions
Color deconfinement and chiral-symmetry restoration have long been predicted by QCD theory. Color deconfinement in the form of a nearly perfect fluid of quarks was reported by all four RHIC experiments in 2005. In a December 2024 paper, the PHENIX Collaboration details two-pion Lévy-stable Bose-Einstein correlation data in Au+Au collisions at the top RHIC energy and reports a significant reduction of the mass of the 𝜂′ meson in hot and dense hadronic, color-confining matter. This implies an indirect observation of a second transition in QCD by the return of the so-called prodigal Goldstone boson—a specific kind of partial chiral-symmetry restoration—and calls for further, challenging experimental studies, aiming at direct measurements of identified 𝜂′ spectra in high-energy heavy-ion collisions.
Reference:
N. J. Abdulameer et al. (PHENIX Collaboration)
Phys. Rev. C 110, 064909 (2024)Speaker: Tamas Csorgo (MATE Institute of Technology Karoly Robert Campus (HU)) -
47
Heavy exotic states at the BESIII experiment
In recent years, a number of charmonium-like states have been observed
above the open-charm threshold in various experiments. Their properties often go
against our expectations for regular charmonium states, making their
interpretation difficult. With BESIII, we are a leading contributor to the
experimental studies of the so-called XYZ states – studying Y-states directly in
e+e- annihilation, while producing X and Z states in hadronic and radiative
transitions. In this talk, recent highlights from the BESIII program on
charmonium(-like) states above the open-charm threshold will be discussed.Speaker: Zhi-yong Wang (IHEP,CAS) -
48
Recent Hadron Spectroscopy results from the Belle and the Belle II experiments
The Belle II experiment, a major upgrade of the Belle experiment, is currently collecting data. With an integrated luminosity of 575 fb-1, Belle II exceeded the maximum integrated luminosity reached by both BaBar and Belle experiments. Recently, data analyses combining Belle and Belle II data were performed, delivering excellent results with unprecedented precision.
In this talk, recent results from hadron spectroscopy will be presented. Results in bottomonium and charmonium physics will be shown, focusing on the Y(10753), the search for pentaquarks, and the new baryon spectroscopy analyses, emphasizing the Omega(2012) and Lambda_c excited states and the search for charmonium states. A prospect on the spectroscopy analysis with combined Belle and Belle II data sets will be introduced as the conclusion of this talk.Speaker: Elisabetta Prencipe -
49
Three-particles scattering with arbitrary angular momentum
In this talk I will present a relativistic formalism for three-particle scattering with arbitrary angular momentum, developed from the integral equations that can be used in lattice QCD analyses. Focusing on spinless systems, I present the partial-wave projected scattering amplitudes that preserve S-matrix unitarity and give simplified expressions for short-distance three-body interactions in both symmetric and asymmetric formalisms. The asymmetric formulation further allows parametrizations suitable for amplitude analyses. To illustrate the framework, I apply it to toy models of three-pion systems at heavy pion masses and different total isospins.
Speaker: Caroline Silva Rocha Costa (LBNL and UC Berkeley)
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46
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12:50
Lunch break
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Hadron spectroscopy
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50
Coalescence production of sexaquark (uuddss) in high-energy collisions
The sexaquark is a stable state with quark content ( u u d d s s) hypothesized by [1] which might be a candidate for dark matter in the Universe. We present results [2] on the coalescence production of the sexaquark using the parton and hadron cascade model PACIAE in p+p collisions at sqrt(s) = 7 TeV. The yields, yield ratios, and dependences of the spatial parameters (the size of the diquark D 0 and the radius of the sexaquark R 0) of a (anti)sexaquark are predicted. The yields of the hadronic H-dibaryon molecule H ( Λ Λ) generated in the final hadronic state are also compared. These estimates provide references for future sexaquark searches and other exotic state studies, such as dibaryons.
[1] Stable Sexaquark, Glennys R. Farrar(New York U., CCPP), e-Print: 1708.08951
[2] Coalescence production of sexaquark with three diquarks in high-energy nuclear collisions, Zhi-Lei She(Wuhan Textile U.) et al., Phys.Rev.D 112 (2025) 3, 034002 • e-Print: 2502.17381 [hep-ph]Speaker: Sonia Kabana (Instituto De Alta Investigación, Universidad de Tarapacá (CL))
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Forward and diffractive physics: (3)
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Review on UPC results from ATLAS and CMS
We will present a review of recent ultraperipheral collisions from the ATLAS and CMS results.
Speaker: Austin Alan Baty (University of Illinois Chicago) -
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UPC Physics at the ALICE Experiment
Ultra-peripheral collisions (UPCs) at the LHC offer a clean and controlled environment to study photon-induced interactions in the absence of hadronic interactions from collision with nuclear overlap. The ALICE experiment has established a comprehensive UPC physics program spanning QCD, electroweak, and nuclear structure studies.
The photoproduction of light vector mesons, such as $\rho^{0}$, $\phi$, and $K^{*0}$, has gained renewed interest, especially in the context of soft QCD and azimuthal anisotropy. In Pb--Pb and Xe--Xe collisions, coherent $\rho^{0}$ photoproduction shows signatures of impact-parameter-dependent modulation and quantum interference at femtoscopic scales.
New Run~3 data enable further differential studies, e.g.\ in $|t|$, the momentum transfer from the target nucleus and electromagnetic dissociation (EMD) classes, allowing improved sensitivity to nuclear shadowing and initial-state geometry. ALICE has also reported measurements of inclusive charm and strangeness photoproduction in Run~3, revealing insights into photonuclear particle production mechanisms.
ALICE is also advancing the study of exclusive multi-hadron final states and investigating baryon-to-meson ratios in inclusive UPCs to explore potential collective behavior in small systems. In the electroweak sector, photon-photon interactions ($\gamma\gamma \rightarrow \tau^{+}\tau^{-}$) are being exploited to probe the anomalous magnetic moment of the tau lepton.
Looking ahead, the upcoming FoCal detector upgrade will allow access to gluon distributions down to Bjorken-$x \sim 10^{-6}$ via direct photon and vector meson production at forward rapidity, significantly extending the UPC program in Run~4.
This talk will provide a comprehensive perspective on the current status, recent breakthroughs, and future opportunities in UPC physics at ALICE.
Speaker: Anisa Khatun (Universita degli studi di Foggia (IT)) -
53
Gluon saturation effects in exclusive heavy vector meson and in $c \bar{c}$, $b \bar{b}$ photoproduction
We study exclusive $J/\Psi$,$\Upsilon$, and $c \bar{c}$, $b \bar{b}$ photoproduction for proton and Pb targets in the high-energy limit, with the energy dependence computed using the linear Balitsky-Fadin-Kuraev-Lipatov and the nonlinear Balitsky-Kovchegov evolution equations. The difference between these two evolution equations can be directly attributed to gluon saturation physics. We find that for proton targets there is no difference between the two approaches at the energies of the currently available data, while for Pb targets data shows a clear preference for the evolution with gluon saturation, showing clear evidence for satiration effects at the LHC in heavy ion data.
Speaker: Christophe Royon (The University of Kansas (US))
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51
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17:00
Coffee / Tea break
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Forward and diffractive physics: (1)
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54
Geometric scaling of elastic pp cross section at the LHC
In this talk we argue that geometric scaling conjectured and observed at
the ISR more than 50 years ago, still holds at the LHC. We discuss
regularities of the dip-bump structures of the differential elastic cross sections, emphasizing the fact that the ratio of bump to dip positions
is constant from the ISR to the LHC. Applying crossing and analyticity we
identify imaginary and real parts of the scattering amplitude and compute the $\rho$ parameter and the ratio of bump to dip values of the differential $pp$ cross section. We also discuss the energy dependence of the total elastic cross section and the violation of geometrical scaling outside the dip-bump region at the LHC.Speaker: Michal Praszalowicz (Jagiellonian University, Krakow)
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Collectivity in high energy collisions: jets, flows, and other mechanisms: (2)
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Light ions at the LHC: early results from the Oxygen and Neon runs and future prospects
In July 2025, the LHC successfully carried out its first light-ion collision programme, delivering substantial luminosities for proton–oxygen, oxygen–oxygen, and neon–neon collisions across the LHC experiments. These new datasets offer unique opportunities to study the quark–gluon plasma in lighter nuclear systems and to explore the role of initial-state configurations in nuclear collisions.
In this talk, I will review early results obtained by different LHC experiments using the light-ion data, covering topics such as collectivity, nuclear modification of hard probes, and beam transmutation effects. I will also discuss how this pioneering run is shaping the future of the ion programme at the High-Luminosity LHC, including new possibilities enabled by accelerator upgrades. These developments open up new experimental avenues for ion physics at CERN, providing unique opportunities to deepen our understanding of the nature of the strong force across different temperature regimes.Speaker: Riccardo Longo (Univ. Illinois at Urbana Champaign (US)) -
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Comparing Tsallis and Boltzmann temperatures in relativistic HICs at intermediate energies by
A+A collisions at BES RHIC energies were generated in UrQMD and SMASH MC Models and compared with results in the box with periodic boundary conditions.
The comparison of pt spectra of different particles with Boltzmann and Tsallis distributions at different time slices has been done.
Our study indicates that - Tsallis distribution better matches the particle pT –spectra both for the matter in the cell and the infinite nuclear matter - UrQMD: parameter q varies from 1.02 to 1.15 for the cell and from 1.01 to 1.07 for the box calculations - SMASH: parameter q varies from 0.99 to 1.07 for the cell and is about 𝟏 ± 𝟎. 𝟎𝟏 for the box calculations - qcell is close to qbox at lower energies for both models - at higher energies the agreement worsens - the Tsallis fit provides (a bit) lower temperatures than the Boltzmann fit both in the cell and in the box calculations.Speaker: Larisa Bravina
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Remembering Laszlo Jenkovszky and Yogiro HamaSpeaker: Tamas Csorgo (MATE Institute of Technology Karoly Robert Campus (HU))
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Meeting of the ISMD Board of Elders: (by invitation)
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20:00
Conference dinner (Greek night, details tba)
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Forward and diffractive physics: (4)
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Review about Color Glass Condensate
This talk will present a review of color glass condensate models, and also the phenomenology how to probe them using existing and incoming data.
Speaker: Florian Cougoulic -
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SIDIS in the forward rapidity region
We calculate the Next to Leading Order (NLO) corrections to single inclusive hadron production in DIS (SIDIS) in the forward rapidity region using the Color Glass Condensate (CGC) formalism. We then consider the kinematic region where the transverse momentum of the produced hadron is much less than the virtuality of the photon and show that there are large (Sudakov) logs originating from this kinematics. We then proceed to derive the Collins-Soper-Sterman (CSS) evolution equation using the background field methods employed in the CGC formalism.
Speaker: Jamal Jalilian-Marian -
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DIS dijet production at subeikonal order and its back-to-back limit
In this talk, I will discuss the back-to-back limit of the DIS dijet production at next-to-eikonal accuracy computed in a highly boosted gluon background field within the Color Glass Condensate (CGC) framework.
I will show that the various types of next-to-eikonal corrections can be written as field strength insertions on the CGC Wilson lines which provide direct relation with the gluon TMDs defined from the two-point correlators of the field strength.
I will then discuss the interplay between the subeikonal corrections in the CGC and the higher twist corrections in the TMD factorization.
Speaker: Alina Czajka (National Centre for Nuclear Research) -
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Gluon saturation in stopping and particle production
In relativistic heavy-ion collisions, stopping in the initial collision stages is accompanied by a local thermalization of gluons towards the Bose-Einstein distribution, and of valence quarks towards the Fermi-Dirac limit. Whereas the thermalization can be accounted for by an analytically solvable nonlinear diffusion model [1], we describe the time-dependent slowing down (``stopping") of the fragments [2] based on a QCD-inspired model for the interaction of valence quarks and soft gluons in the respective other nucleus. For data in the expected stopping-peak region at LHC that could determine the gluon saturation scale, a new forward-spectrometer would be needed to distinguish protons from pions and kaons. Charged-hadron production in symmetric (Pb-Pb) and asymmetric (p-Pb) collisions also depends on the gluon saturation scale Q_s, and we investigate its centrality dependence in p-Pb at sqrt(s_NN)=5.02 and 8.16 TeV [3].
[1] G. Wolschin, EPL 140, 40002 (2022)
[2] J. Hoelck, G. Wolschin, Phys. Rev. Res. 2, 033409 (2020)
[3] P. Schulz, G. Wolschin, Phys. Rev. C110, 044910 (2024)Speaker: Georg Wolschin
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10:40
Coffee / Tea break
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Forward and diffractive physics: (4)
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Central exclusive production of eta and eta' mesons in diffractive proton-proton collisions at the LHC within the tensor-pomeron approach (online)
We present a study of the central exclusive production (CEP) of $\eta$ and $\eta'(958)$ mesons in diffractive proton-proton collisions at high energies. The amplitudes, including pomeron and reggeon exchanges, are calculated within the tensor-pomeron model. Absorption effects are also taken into account at the amplitude level. We fit some undetermined model parameters (coupling constants and cutoff parameters in form factors) to the WA102 experimental data and then make predictions for the LHC energy $\sqrt{s} = 13$ TeV. Both, total cross sections and several differential distributions are presented. For $pp \to pp \eta$, we find an upper limit for the total cross section of 2.5 $\mu$b for pseudorapidity of the $\eta$ meson $|\eta_{M}| < 1$ and 5.6 $\mu$b for $2 < \eta_{M} < 5$. For $pp \to pp \eta'$, we predict the cross section to be in the range of 0.3-0.7 $\mu$b for pseudorapidity of the $\eta'$ meson $|\eta_{M}| < 1$ and 0.9-2.1 $\mu$b for $2 < \eta_{M} < 5$. This opens the possibility to study diffractive production of pseudoscalar mesons in experiments at the LHC. We discuss if there are arguments from SU(3)-flavor symmetry which would forbid pomeron-pomeron fusion giving an $\eta$ meson. In our opinion such arguments do not exist. We also consider CEP of the pseudoscalars $\eta$ and $\eta'(958)$ and the pseudovector meson $f_{1}(1285)$ in diffractive proton-proton collisions in a theory with a scalar pomeron. We show that none of these particles can be produced in this way in the scalar-pomeron theory. Thus, experimental observation of any of these particles in the above CEP processes at the LHC would give striking evidence against a scalar character of the pomeron.
Speaker: Otto Nachtmann (University of Heidelberg) -
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Prospects for measuring exclusive diffractive $\eta,\eta'(958)$ production at the LHC
I present a feasibility study for measuring central exclusive $\eta,\eta' (958)$ production at the LHC. These pseudo-scalar mesons can be detected by their decays $\eta'(958) \rightarrow \pi^+\pi^-\eta$, and $\eta \rightarrow \pi^+\pi^-\pi^0$. For such measurements, the detection of the forward scattered protons is mandatory. I present the required detector position resolution of these very forward detectors for such measurements, and discuss the acceptance for a nominal $\beta^{*}$ = 10m optics, and for possible $\beta^{*}$ values of 20m and 30m.
Speaker: Rainer Schicker (Heidelberg University (DE)) -
64
Diffraction at the LHCb Experiment
The LHCb experiment offers unique capabilities for studying ultra-peripheral collisions (UPCs) and other diffractive processes at the LHC. The forward acceptance of the detector, covering pseudorapidity $2<\eta<5$, allows for the detection of low-mass resonances produced in diffraction as well as kinematic reach down to very low $x$. The particle identification and vertexing capabilities of the detector enable precision measurements of diverse final states within this acceptance, giving access to a wide range of diffractive processes from both protons and heavy nuclei. This talk will provide an overview of recent diffractive results from LHCb, including heavy quarkonium production in UPCs, light hadron spectroscopy, and diffractive production of exotic states.
Speaker: Jackson Reeves Pybus (Los Alamos National Laboratory (US)) -
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Selected photon-proton and photon-nucleus processes at the LHC
We give an overview of the possibilties of studying photon-proton and photon-nucleus processes at the LHC that arise from exploiting the Weizsaecker-Williams flux of quasireal photons. In particular we will discuss diffractive photoproduction on nuclei, inclusive photoproduction of open charm, and prospects of measuring the total photoabsorption cross section at very high energies.
Speaker: Wolfgang Schaefer
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62
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12:50
Lunch break
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Astroparticle physics and cosmology: (2)
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66
Impact of the 2nd Generation of post-LHC Hadronic Interaction Models on Air Shower Simulations
The interpretation of extensive air shower (EAS) measurements strongly depends on detailed air shower simulations. CORSIKA is one of the most commonly used air shower Monte Carlo program. The main source of uncertainty in the prediction of shower observables for different primary particles and energies being currently dominated by differences between hadronic interaction models even after the update taking into account the first LHC data. As a matter of fact the model predictions converged but at the same type more precise air shower and LHC measurements introduced new constraints. This year a new generation of hadronic interaction models is released in CORSIKA. QGSJETIII-01 and EPOS.LHC-R are now available with improved description of particle production and in particular the forward production. The impact of these hadronic interaction models on air shower predictions will be presented and compared to the first generation of post-LHC models EPOS LHC, QGSJETII-04 and Sibyll 2.3e. Due to the various approach in the physics treatment, there is still large differences in the model predictions both in the description of LHC data and the interpretation of cosmic ray measurements.
Speaker: Dr Tanguy Pierog -
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From Space to Extensive Air Showers: the Journey of Ultra-High-Energy Cosmic Rays as Measured by the Pierre Auger Observatory
The origin and nature of cosmic rays in the EeV energy range remain one of the major open questions in astroparticle physics. Their energies far exceed those attainable by human-made accelerators, and their extremely low flux makes direct detection by space-based instruments unfeasible. For over two decades, the Pierre Auger Observatory—a 3000 km² array of instruments spread across the Argentinean pampa—has been recording extensive air showers resulting from the interaction of ultra-high-energy cosmic rays with the atmosphere, using a hybrid detection approach that combines multiple, complementary measurement techniques.
Detailed measurements of the longitudinal shower profile and the spatial distribution of secondary particles at ground level provide valuable insights into the cosmic-ray energy spectrum, anisotropies, and composition. In this talk, we present some of the latest results from the Pierre Auger Observatory related to these key measurements, along with recent findings on hadronic interactions and muon content.
With the recent upgrade of the Observatory, AugerPrime — aimed primarily at improving the characterization of the muonic component — and its extended operation through 2035, a wealth of new and unique measurements is anticipated in the coming years.Speaker: Kevin Cheminant (Radboud University / NIKHEF)
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66
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16:10
Coffee / Tea break
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Astroparticle physics and cosmology: (3)
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68
Updated Measurement of the Proton-Proton Interaction Cross-Section at Ultrahigh Energies with the Pierre Auger Observatory
The measurement of hadronic interaction cross-sections at the highest cosmic-ray energies provides a unique opportunity to probe soft QCD processes beyond the reach of existing accelerator experiments. A key observable for such studies is the atmospheric depth at which air showers reach their maximum development ($X_\mathrm{max}$), which is sensitive to both the mass of the primary cosmic rays and the particle interaction cross-section.
In this contribution, we present a measurement of the inelastic proton-proton cross-section at ultrahigh energies using data collected by the Fluorescence Detector of the Pierre Auger Observatory, based on a method that simultaneously fits the proton-proton cross-section, primary mass composition, and the $X_\mathrm{max}$ scale. This approach addresses the challenges of earlier analyses that inferred the cross-section from the tail of the $X_\mathrm{max}$ distribution by directly considering the interdependence between the three estimated quantities.
The measured cross-section is consistent with extrapolations from accelerator data, previous estimates from cosmic-ray data, and the results obtained from a tail-fit applied to the same dataset. In comparison with previous analyses, the current approach provides reduced overall uncertainties and extends the cross-section analysis to higher energies. The inferred mass composition is somewhat heavier than in earlier analyses, and the fitted $X_\mathrm{max}$ scale exhibits a small shift relative to model predictions. Overall, the results remain in agreement with previous estimates within the quoted systematic uncertainties, while offering improved precision and a weaker dependence on assumptions related to the mass composition and hadronic interaction models.
Speaker: Dr Olena Tkachenko (Institute of Physics of the Czech Academy of Sciences) -
69
Modified predictions of hadronic interaction models suggesting a Heavy-metal scenario of ultra-high-energy cosmic rays
The search for origin of the most energetic cosmic rays has been mainly obscured by uncertainties in their mass composition arising from the modelling of hadronic interactions in the air showers that these particles induce. For some time now, discrepancies between the model predictions and measured air-shower data have been complicating efforts to find a consistent mass-composition scenario of ultra-high-energy cosmic rays (UHECR, above $10^{18}$ eV). A deficit of the simulated signal relative to the measured signal in ground detectors is an inconsistency that is usually interpreted as a deficit of the muon signal induced by the hadronic component of a simulated shower. Recent advances in testing models of hadronic interactions revealed a new problem in the predicted scale of the depth of shower maximum ($X_\text{max}$), which is usually considered as the best estimator of the cosmic-ray mass. The $X_\text{max}$ scale seems to be significantly underestimated in most of the hadronic interaction models.
I will briefly review tests of models of hadronic interactions using UHECR data implying that the predicted $X_\text{max}$ scale could be at a level that is consistent with a very heavy mass composition at the highest energies. I will also introduce the MOdified Characteristics of Hadronic Interactions (MOCHI) project, which aims to explore the phase space of combinations of modifications in the cross section, multiplicity and elasticity of hadronic interactions to find qualitative directions of modifications that could explain the discrepancies between the UHECR measurements and model predictions. Finally, I will introduce an extreme Heavy-metal scenario of UHECR assuming pure iron nuclei in the flux-suppression region (above $10^{19.6}$ eV). Such a scenario might be a viable option in the nature given the recent advances in the air-shower modelling.
Speaker: Dr Jakub Vicha (Institute of Physics of the Czech Academy of Sciences) -
70
Mapping multiparticle production variables of primary proton-air interactions onto extensive air shower observables
Extensive air showers (EAS) triggered by ultra-high-energy cosmic rays (UHECRs) are driven by hadronic interactions with low momentum transfer, which cannot be described by perturbative QCD. Moreover, the phenomenological models employed in simulating such interactions lack constraints from accelerator measurements in the relevant phase-space region for shower development. This leads to large model uncertainties that hamper the mass interpretation of the cosmic-ray flux.
In this contribution, we introduce a set of multiparticle production variables that enable mapping the energy spectrum of secondary hadrons produced in the cosmic-ray–air interaction onto the joint distribution of key EAS observables: the depth of the shower maximum and the muon content at ground level. We quantify the precision of this mapping and demonstrate independence on the underlying hadronic interaction model, enabling constraints on secondary-hadron energy spectra directly from EAS data at kinematic regimes inaccessible to present human-made colliders.
Furthermore, we show that these production variables can be measured within the kinematic acceptance of existing particle colliders, and that their predicted distributions exhibit maximal separation between models in precisely the region most relevant for shower evolution.Speaker: Miguel Martins
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