Pionic depth of the hadron gas after a heavy-ion collision

TL;DR

This paper models the likelihood of pions rescattering in the hadron gas after heavy-ion collisions, revealing a high probability around 0.5 GeV and quantifying the fraction of pions that escape without interaction.

Contribution

It provides the first theoretical computation of the pionic depth in the hadron gas using advanced pion interaction parametrizations, linking rescattering probabilities to collision dynamics.

Findings

High rescattering probability (~50%) at p_T=0.5 GeV

10-24% of pions escape without interaction

Comparison of collision and expansion rates

Abstract

The final stage of a relativistic heavy-ion collision is a hadron gas. Final-state interactions therein distort the $p_T$ spectrum of particles coming from the phase transition upon cooling the quark-gluon plasma. Using recent state-of-the-art parametrizations of pion interactions we provide theoretical computations of the pionic depth of the gas: how likely is it that a given pion rescatters in it (we find a high probability around $p_T=0.5$ GeV at midrapidity, corresponding to the formation of the $\rho$ resonance), a comparison of the collision and Bjorken expansion rates, and how many pions make it through without interacting as a function of $p_T$. This is in the range 10-24$\%$ and shown in this plot, the main result of the contribution.