Freezeout systematics due to the hadron spectrum

TL;DR

This study examines how uncertainties in the hadron spectrum affect the determination of the freezeout surface in heavy ion collisions, finding that certain thermal parameters are robust while flavor hierarchy hints persist.

Contribution

It introduces a systematic analysis of the impact of unconfirmed resonance states on freezeout parameters in heavy ion collision models.

Findings

Freezeout temperature drops by ~5% with spectrum uncertainties.

Dimensionless parameters like μ_B/T and VT^3 are insensitive to spectrum systematics.

Flavor hierarchy in freezeout parameters remains evident despite uncertainties.

Abstract

We investigate systematics of the freezeout surface in heavy ion collisions due to the hadron spectrum. The role of suspected resonance states that are yet to be confirmed experimentally in identifying the freezeout surface has been investigated. We have studied two different freezeout schemes - unified freezeout scheme where all hadrons are assumed to freezeout at the same thermal state and a flavor dependent sequential freezeout scheme with different freezeout thermal states for hadrons with or without valence strange quarks. The data of mean hadron yields as well as scaled variance of net proton and net charge distributions have been analysed. We find the freezeout temperature $T$ to drop by $\sim5\%$ while the dimensionless freezeout parameters $\mu_B/T$ and $VT^3$ ($\mu_B$ and $V$ are the baryon chemical potential and the volume at freezeout respectively) are insensitive to the systematics of the input hadron spectrum. The observed hint of flavor hierarchy in $T$ and $VT^3$ with only confirmed resonances survives the systematics of the hadron spectrum. It is more prominent between $\sqrt{s_{NN}}\sim10 - 100$ GeV where the maximum hierarchy in $T\sim10\%$ and $VT^3\sim40\%$. However, the uncertainties in the thermal parameters due to the systematics of the hadron spectrum and their decay properties do not allow us to make a quantitative estimate of the flavor hierarchy yet.