Köln 2025 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 3: Heavy-Ion Collisions and QCD Phases I

HK 3.5: Talk

Monday, March 10, 2025, 16:00–16:15, HS 3 Chemie

Study of the heavy-quark out-of-equilibrium distribution function — •Rossana Facen — Physikalisches Institut Heidelberg, Heidelberg, Germany

Heavy quarks, i.e. charm and bottom, are unique probes to study the properties of the quark-gluon plasma (QGP). Due to their large masses, heavy quarks are produced at the initial stage of the collision almost exclusively via hard partonic scattering and experience the entire collision history.
Even if the heavy-quark distribution function is out of equilibrium, a fluid-dynamic approach has been demonstrated to be applicable to study the dynamics of charm quarks in the QGP [1]. However, out-of-equilibrium (ooe) corrections of the heavy-quark distribution function must be considered at the freeze-out, to correctly compute charm-hadron momentum distributions and integrated yields. In order to parameterize the ooe corrections, two different theoretical frameworks have been proposed. The Multi-Fluid description, a microscopic approach arising from kinetic theory, assumes that multiple species contribute to the diffusion of heavy quarks. On the other hand, the Maximum Entropy method is based on macroscopic considerations, and computes the ooe distribution maximizing the entropy current. In this work, we study the validity of these two approaches, focusing on their feasibility to describe heavy-quark dynamics.
This work is funded via the DFG ISOQUANT Collaborative Research Center (SFB 1225).

[1] Phys.Rev.D 106 (2022) 3, 034021

Keywords: Heavy Quark; Out-of-Equilibrium Distribution Function