# Kinetic freeze-out in central heavy-ion collisions between 7.7 and 2760 GeV per nucleon pair

## TL;DR

This study analyzes particle momentum spectra from heavy-ion collisions across a wide energy range using a blast wave model, revealing how freeze-out temperature and expansion velocity vary with collision energy.

## Contribution

It introduces a comprehensive fit of $p_t$ spectra using a Gaussian emulator with resonance effects and partial chemical equilibrium, covering energies from 7.7 to 2760 GeV.

## Key findings

- Freeze-out temperature decreases from 100 MeV to 80 MeV with increasing energy.
- Average transverse expansion velocity increases from 0.45 to 0.65.
- Resonance decay influence is minimal above 27 GeV.

## Abstract

We fit the single-particle $p_t$ spectra of identified pions, kaons, and (anti)protons from central collisions of gold or lead nuclei at energies between 7.7 and 2760~GeV per nucleon pair. Blast wave model with included resonance production and with an assumption of partial chemical equilibrium is used and the fits are performed with the help of a Gaussian emulator process. A kinetic freeze-out temperature is found about 100~MeV for the lowest collision energies and 80~MeV at the LHC. The average transverse expansion velocity grows with increasing $\sqrt{s_{NN}}$ from 0.45 to 0.65. Due to partial chemical equilibrium, the influence of resonance decays on the shape of the $p_t$ spectra for $\sqrt{s_{NN}}$ above 27~GeV is small.