Effects of partial thermalization on HBT interferometry

TL;DR

This study investigates how partial thermalization affects HBT interferometry radii in heavy-ion collisions, using a transport model to bridge the gap between hydrodynamics and experimental data, addressing the HBT puzzle.

Contribution

It introduces a systematic analysis of HBT radii dependence on thermalization degree via a transport model, providing insights into the HBT puzzle.

Findings

R_o/R_s ratio closer to experimental data at realistic Knudsen numbers

Femtoscopic observables show little variation with thermalization degree

Azimuthal oscillations are not effective probes of thermalization

Abstract

Hydrodynamical models have generally failed to describe interferometry radii measured at RHIC. In order to investigate this ``HBT puzzle'', we carry out a systematic study of HBT radii in ultrarelativistic heavy-ion collisions within a two-dimensional transport model. We compute the transverse radii $R_o$ and $R_s$ as functions of $p_t$ for various values of the Knudsen number, which measures the degree of thermalization in the system. For realistic values of the Knudsen number estimated from $v_2$ data, we obtain $R_o/R_s \simeq 1.2$, much closer to data than standard hydrodynamical results. Femtoscopic observables vary little with the degree of thermalization. Azimuthal oscillations of the radii in non central collisions do not provide a good probe of thermalization.