The effect of "pre-formed" hadron potentials on the dynamics of heavy ion collisions and the HBT puzzle

TL;DR

This paper demonstrates that incorporating potentials for 'pre-formed' particles in the UrQMD model improves the simulation of heavy ion collision observables, resolving the HBT puzzle across multiple energy ranges.

Contribution

It introduces a novel approach of including potentials for 'pre-formed' particles in transport models, enhancing the accuracy of heavy ion collision simulations.

Findings

Better agreement with experimental data for nuclear stopping and elliptic flow.

Resolution of the HBT puzzle by adjusting the radii R_O and R_S.

Consistent description across AGS, SPS, and RHIC energies.

Abstract

The nuclear stopping, the elliptic flow, and the HBT interferometry are calculated by the UrQMD transport model, in which potentials for "pre-formed" particles (string fragments) from color fluxtube fragmentation as well as for confined particles are considered. This description provides stronger pressure at the early stage and describes these observables better than the default cascade mode (where the "pre-formed" particles from string fragmentation are treated to be free-streaming). It should be stressed that the inclusion of potential interactions pushes down the calculated HBT radius $R_O$ and pulls up the $R_S$ so that the HBT time-related puzzle disappears throughout the energies from AGS, SPS, to RHIC.