Pion freeze-out through HBT correlation in HICs from AGS/FAIR to RHIC energies

TL;DR

This study analyzes two-pion HBT correlations at freeze-out in heavy ion collisions across a wide energy range using the UrQMD model, highlighting successes and ongoing discrepancies with experimental data.

Contribution

It applies the UrQMD model and CRAB analysis to systematically study pion freeze-out characteristics from AGS to RHIC energies, addressing the HBT puzzle.

Findings

Calculations align with experimental data but have notable discrepancies.

The HBT time-related puzzle persists at all energies.

At low energies, the model underestimates the source volume and mean free path.

Abstract

In this talk we present the results of two-pion HBT correlation at freeze-out in heavy ion collisions (HICs) from AGS to RHIC energies. The UrQMD hadron-string transport model as well as the CRAB analyzing program are adopted. Based on the cascade mode, in general, the calculations are satisfying and well in line with the experimental data although discrepancies are not negligible. Such as: I), the HBT time-related puzzle exists at all energies. II), at low AGS energies, the calculated volume as well as the mean free path of pion source at freeze-out are lower than data. It implies that a better description of interactions of particles at early stage of HICs is required.