Effect of Hagedorn states on isothermal compressibility of hadronic matter formed in heavy-ion collisions: From NICA to LHC energies

Abstract

In this work, we have studied the isothermal compressibility (κT) as a function of temperature, baryon chemical potential, and center-of-mass energy (sNN) using hadron resonance gas (HRG) and excluded-volume hadron resonance gas (EV-HRG) models. A mass cut-off dependence of isothermal compressibility has been studied for a physical resonance gas. Further, we study the effect of heavier resonances (>2GeV) on the isothermal compressibility by considering the Hagedorn mass spectrum, ρ(m)∼exp(bm)/(m2+m02)5/4. Here the parameters b and m0 are extracted after comparing the results of recent lattice QCD simulations at finite baryonic chemical potential. We find a significant difference between the results obtained in EV-HRG and HRG models at higher temperatures. The inclusion of the Hagedorn mass spectrum in the partition function for hadron gas has a large effect at a higher temperature. A higher mass cut-off in the Hagedorn mass spectrum takes the isothermal compressibility to a minimum value, which occurs near the Hagedorn temperature (TH). We show explicitly that at the future low-energy accelerator facilities like FAIR (CBM), Darmstadt, and NICA, Dubna, the created matter would have higher compressibility compared to the high-energy facilities like the Relativistic Heavy Ion Collider and Large Hadron Collider. © 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.