Phase transition amplification of proton number fluctuations in nuclear collisions from a transport model approach

TL;DR

This study uses a transport model to investigate how a phase transition influences proton number fluctuations in nuclear collisions, revealing a significant fluctuation enhancement linked to unstable regions, with implications for experimental observables.

Contribution

It introduces a transport model incorporating a first order phase transition to study fluctuation dynamics in nuclear collisions, highlighting the phase transition's impact on baryon number fluctuations.

Findings

Significant fluctuation enhancement during unstable phase regions.

Fluctuation memory persists to late times.

Minimal impact on proton fluctuations in momentum space.

Abstract

The time evolution of particle number fluctuations in nuclear collisions at intermediate energies ($E_{\rm lab} = 1.23-10A$ GeV) is studied by means of the UrQMD-3.5 transport model. The transport description incorporates baryonic interactions through a density-dependent potential. This allows for an implementation of a first order phase transition including a mechanically unstable region at large baryon density. The scaled variance of the baryon and proton number distributions is calculated in the central cubic spatial volume of the collisions at different times. A significant enhancement of fluctuations associated with the unstable region is observed. This enhancement persists to late times reflecting a memory effect for the fluctuations. The presence of the phase transition has a much smaller influence on the observable event-by-event fluctuations of protons in momentum space.