Analytical insights into the interplay of momentum, multiplicity, and the speed of sound in heavy-ion collisions

by Jean-Francois Paquet (Vanderbilt University)

Tuesday 25 Mar 2025, 11:00 → 13:00 US/Eastern

CFNS/Physics Library

There have been recent proposals that the speed of sound of quark-gluon plasma can be measured from multiplicity and mean transverse momentum ($p_T$) measurements in ultracentral heavy-ion collisions, based on thermodynamics arguments and numerical simulations [1]. The CMS Collaboration has used this approach to extract values of the speed of sound remarkably consistent with lattice QCD calculations [2]. We use a minimal model of ultracentral heavy-ion collisions based inviscid relativistic hydrodynamics to study the relation between the speed of sound and the hadronic multiplicity and mean $p_T$. We find a non-trivial relation between the speed of sound and multiplicity-mean $p_T$ correlations with a clear dependence on the system's lifetime [3]. Dependence on initial conditions, as well as $p_T$ and rapidity cuts, will also be discussed.