Effect of hadronic cascade time on freeze-out properties of Identified Hadrons in Au+Au Collisions at $\sqrt{s_{NN}}$ = 7.7-39 GeV from AMPT Model

TL;DR

This study uses the AMPT model to analyze how hadronic cascade time affects freeze-out properties of identified hadrons in Au+Au collisions across various energies, finding minimal impact on spectra and freeze-out parameters.

Contribution

It introduces a detailed analysis of hadronic cascade time effects on freeze-out properties using AMPT-SM, with improved agreement to experimental data and exploration at energies lacking data.

Findings

No significant effect of cascade time variation on $p_T$ spectra.

Freeze-out temperature increases from central to peripheral collisions.

Strong anti-correlation between $T_{kin}$ and $<eta_T>$.

Abstract

We report the transverse momentum $p_T$ spectra of identified hadrons ($\pi^\pm$, $K^\pm$ and $p(\bar p)$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 39 GeV from A Multi Phase Transport Model with string melting effect (AMPT-SM). During this study, a new set of parameters are explored to study the effect of hadronic cascade by varying hadronic cascade time $t_{max}$ = 30 $f$m/$c$ and 0.4 $f$m/$c$. No significant effect of this change is observed in the $p_T$ spectra of light hadrons and the AMPT-SM model reasonably reproduces the experimental data. To investigate the kinetic freeze-out properties the blast wave fit is performed to the $p_T$ spectra and it is found that the blast wave model describes the AMPT-SM simulations well. We additionally observe that the kinetic freeze-out temperature ($T_{kin}$) increases from central to peripheral collisions, which is consistent with the argument of short-lived fireball in peripheral collisions. Whereas the transverse flow velocity, $<\beta_T>$ shows a decreasing trend from central to peripheral collisions indicating a more rapid expansion in the central collisions. Both, $T_{kin}$ and $<\beta_T>$ show a weak dependence on the collision energy at most energies. We also observe a strong anti-correlation between $T_{kin}$ and $<\beta_T>$. The extracted freeze-out parameters from the AMPT-SM simulations agree with the experimental data as opposed to earlier studies that reported some discrepancies. Whereas, no significant effect is found on the freeze-out parameters by varying the $t_{max}$. We also report the $p_T$ spectra of light hadrons and their freeze-out parameters by AMPT-SM simulations at $\sqrt{s_{NN}}$ = 14.5 GeV, where no experimental data is available for comparison. Overall, the set of parameters used in this study well describes the experimental data at BES energies.