Nuclear interactions and net-proton number fluctuations in heavy ion collisions at the SIS18 accelerator

TL;DR

This paper investigates how nuclear interactions influence net-proton fluctuations in heavy ion collisions at SIS18, revealing that nuclear forces enhance cumulants but are mitigated by conservation laws and isospin effects.

Contribution

It demonstrates the impact of nuclear forces on baryon number fluctuations using the UrQMD model, accounting for conservation laws and isospin effects in heavy ion collisions.

Findings

Nuclear forces increase baryon number cumulants.

Isospin randomization and conservation laws reduce fluctuation signals.

Global baryon number conservation dominates for large rapidity windows.

Abstract

The effect of nuclear interactions on measurable net-proton number fluctuations in heavy ion collisions at the SIS18/GSI accelerator is investigated. The state of the art UrQMD model including interaction potentials is employed. It is found that the nuclear forces enhance the baryon number cumulants, as predicted from grand canonical thermodynamical models. The effect however is smeared out for proton number fluctuations due to iso-spin randomization and global baryon number conservation, which decreases the cumulant ratios. For a rapidity acceptance window larger than $\Delta y> 0.4$ the effects of global baryon number conservation dominate and all cumulant ratios are significantly smaller than 1.