Specific Heat of Matter Formed in Relativistic Nuclear Collisions

TL;DR

This study measures the specific heat of hadronic matter in relativistic nuclear collisions, revealing a sharp increase below 62.4 GeV and comparing results with the Hadron Resonance Gas model and other theories.

Contribution

It provides the first detailed excitation energy dependence of specific heat at freeze-out in heavy-ion collisions, using event-by-event temperature fluctuations.

Findings

Sharp rise in specific heat below 62.4 GeV collision energy

Good agreement between experimental data and Hadron Resonance Gas model

Predictions for specific heat at LHC energies

Abstract

We report the excitation energy dependence of specific heat (\cv) of hadronic matter at freeze-out in Au+Au and Cu+Cu collisions at the Relativistic Heavy Ion Collider energies by analyzing the published data on event-by-event mean transverse momentum (\meanpt) distributions. The \meanpt~distributions in finite \pt~ranges are converted to distributions of effective temperatures, and dynamical fluctuations in temperature are extracted by subtracting widths of the corresponding mixed event distributions. The heat capacity per particle at the kinetic freeze-out surface is presented as a function of collision energy, which shows a sharp rise in \cv~below \sNN~=~62.4~GeV. We employ the Hadron Resonance Gas (HRG) model to estimate \cv~at the chemical and kinetic freeze-out surfaces. The experimental results are compared to the HRG and other theoretical model calculations. HRG results show good agreement with data. Model predictions for \cv~at the Large Hadron Collider energy are presented.