5th International Workshop on Emergent QCD Collectivity Across Scales: From Small System Collisions to Jets

Europe/Paris
Rice Global Paris Center

Rice Global Paris Center

Matthew Nguyen (Centre National de la Recherche Scientifique (FR)), Prabhat Ranjan Pujahari (Indian Institute of Technology Madras (IN)), Wei Li (Rice University (US)), Xiaoyu Liu (Rice University (US))
Description

This workshop is the fifth edition of the International Small Systems workshop series, continuing a focused effort to understand how collective phenomena emerge in Quantum Chromodynamics (QCD).

Building on the progress of previous meetings, this edition expands the discussion from small collision systems to jets and other multi-scale probes, reflecting the recent evolution of the field. Recent collider measurements have revealed signatures of collectivity in a remarkably wide range of systems, including pp, pA, light-ion, photonuclear and jet-tagged events. These observations challenge traditional distinctions between small and large systems, soft and hard probes, and initial- and final-state dynamics. A central aim of the workshop is to place these developments within a unified, scale-dependent QCD framework, and to clarify what they reveal about the emergence of many-body dynamics from microscopic strong interactions.

The workshop emphasizes that collective phenomena, such as long-range correlations, multiparticle cumulants, jet–medium correlations, polarization effects, and femtoscopic observables, are inherently non-perturbative manifestations of QCD. While perturbative methods successfully describe the production of hard probes, the emergence of collective behavior reflects strong coupling, coherence, and many-body dynamics. Jets, in particular, occupy a unique position at the interface of perturbative production and non-perturbative response, making them powerful differential probes of emergent QCD matter. In addition to hydrodynamic and kinetic approaches, the workshop also explicitly explores novel perspectives such as quantum correlations and entanglement as complementary ways of organizing multiparticle dynamics.

The goal of the workshop is not consensus, but clarity: to identify robust observations, expose open questions, and encourage bold, forward-looking ideas that may guide future experiments and theory. To preserve its interactive character, the workshop is intentionally small and invitation-only. Talks and discussion sessions are structured to emphasize provocation and debate rather than comprehensive result reporting.

 
 
Participants
    • Welcome
    • Collectivity and Initial States
      Convener: Prabhat Ranjan Pujahari (Indian Institute of Technology Madras (IN))
      • 1
        Probing collectivity in small collision systems with asymmetric d+Au and symmetric O+O collisions
        Speaker: Shengli Huang
      • 2
        Collective flow and hydrodynamization as a function of system size from kinetic theory simulations
        Speaker: Clemens Werthmann (Ghent University)
    • Coffee Break
    • Collectivity and Initial States
      Convener: Prabhat Ranjan Pujahari (Indian Institute of Technology Madras (IN))
      • 3
        Collective Flow Across System Size: An Experimental Perspective from Light Ions to the Smallest Systems
        Speaker: You Zhou (Niels Bohr Institute (DK))
      • 4
        Balance functions as probes of particle production mechanisms
        Speaker: Alice Ohlson (Lund University (SE))
    • 12:10
      lunch
    • Equation of States, Speed of Sound
      Convener: Dr Maxime Guilbaud (Subatech - IMT Atlantique Nantes)
      • 5
        Extracting the speed of sound of QCD from transverse momentum fluctuations
        Speakers: Jean-Yves OLLITRAULT, Jean-Yves OLLITRAULT
      • 6
        Feasibility of measuring the QGP speed of sound from ultracentral heavy-ion collisions
        Speaker: Jean-Francois Paquet (Vanderbilt University)
    • 15:20
      Coffee Break
    • To be collective or not: methods, nonflow, etc.
      Convener: Dr Maxime Guilbaud (Subatech - IMT Atlantique Nantes)
      • 7
        Nonflow Subtraction Beyond Two-Particle Correlations
        Speaker: Jiangyong Jia (Stony Brook University (US))
      • 8
        Methodological Challenges and Possible Solutions for Differential Flow Measurements in Small-System Collisions
        Speaker: Rohit Kumar Singh (Indian Institute of Technology Madras (IN))
    • 18:00
      Reception
    • Vorticity, Polarization, Chiral Condensate
      Convener: Andre Govinda Stahl (CERN)
      • 9
        Polarization & collectivity across scales - correlated or not?
        Speaker: Zhenyu Chen (Shandong University (CN))
      • 10
        Dynamical chiral condensate as a coherent sigma/f_0(500) field
        Speaker: Stefan Floerchinger (University of Jena)
    • 10:20
      coffee break
    • Intra-jet Collectivity, Partonic Transport
      Convener: Andre Govinda Stahl (CERN)
      • 11
        Toward Improved Transport Modeling of Collectivity
        Speaker: Zi-Wei Lin (East Carolina University)
      • 12
        TBD
        Speaker: Xiaoyu Liu (Rice University (US))
    • 12:10
      lunch
    • e+e-, jets, EEC
      Convener: Matthew Nguyen (Centre National de la Recherche Scientifique (FR))
      • 13
        TBD
        Speaker: Yen-Jie Lee (Massachusetts Inst. of Technology (US))
      • 14
        TBD
        Speaker: Carlota Andres (MIT)
    • 15:20
      coffee break
    • Parton Energy Loss, Medium Response, Jet Substrcture
      Convener: Matthew Nguyen (Centre National de la Recherche Scientifique (FR))
      • 15
        To scatter or not to scatter: effects of the first re-scattering
        Speaker: Korinna Zapp
      • 16
        Breakdown of LPM Suppression in Extremely High-Energy Bremsstrahlung
        Speaker: Omar Elgedawy (CPHT, Ecole Polytechnique)
    • 19:00
      Workshop Dinner
    • Heavy Flavor & Small Systems
      Convener: Jing Wang (Massachusetts Inst. of Technology (US))
      • 17
        Heavy Quarks across Scales: QGP, Hadronization & CNM effects
        Speaker: Wei Xie (Purdue University (US))
      • 18
        Light-Ion Physics at LHCb
        Speaker: JiaZhao Lin (Indiana University (US))
    • 10:20
      coffee break
    • Light Ions
      Convener: Jing Wang (Massachusetts Inst. of Technology (US))
      • 19
        Dynamical core-corona initialisation in p+p and O+O collisions
        Speaker: Tetsufumi Hirano
      • 20
        New collectivity measurements of light ions and small systems at CMS
        Speaker: Aryaa Dattamunsi (Indian Institute of Technology Madras (IN))
    • 12:10
      Lunch
    • Light Ions
      Convener: Wei Li (Rice University (US))
      • 21
        The unexpected uses of a bowling pin
        Speaker: Govert Hugo Nijs (CERN)
      • 22
        Studying the nuclear structures with high-energy collisions of light and heavy ions at the LHC
        Speaker: Maxim Virta (University of Jyväskylä)
    • 15:20
      Coffee break
    • Balance Function, Summary, Wrap-ups
      Convener: Wei Li (Rice University (US))
      • 23
        How can we tell if QGP droplets form in Small Systems at RHIC and the LHC?
    • EIC physics and experiment
      • 24
        Fluctuating Proton Geometry: Constraints from Charge Radius, Diffraction, and Flow
        Speaker: Wenbin Zhao (Wayne State University)
      • 25
        DDbar correlations in eA
        Speaker: Cyrille Marquet (CPHT - Ecole Polytechnique)
    • 10:20
      Coffee Break
    • EIC physics and experiment
      • 26
        ePIC experiment
        Speaker: Carlos MUNOZ CAMACHO
      • 27
        EICROC development
        Speaker: Dr Christophe De La Taille (OMEGA (FR))
    • 12:10
      Lunch Break
    • ePIC experiment collaboration: simulation, ASICs, frontend readout etc.
      • 28
        Frontend electronics and DAQ for AC-LGADs: status and plan
        Speaker: Tonko Ljubicic (Rice University)
    • 15:20
      Coffee Break
    • More discussions on ePIC, Closing