Proton correlations and apparent intermittency in the UrQMD model with hadronic potentials

TL;DR

This study shows that including hadronic potentials in UrQMD simulations of heavy ion collisions creates proton correlations that mimic intermittency signals, aligning with experimental observations.

Contribution

It demonstrates that proton correlations from hadronic potentials significantly influence intermittency analysis, providing a new understanding of observed signals in heavy ion collision experiments.

Findings

Proton correlations are enhanced by hadronic potentials.

Intermittency index matches experimental data when nuclear interactions are included.

Correlated proton pairs with small relative momentum drive the apparent intermittency signal.

Abstract

It is shown that the inclusion of hadronic interactions, and in particular nuclear potentials, in simulations of heavy ion collisions at the SPS energy range can lead to obvious correlations of protons. These correlations contribute significantly to an intermittency analysis as performed at the NA61 experiment. The beam energy and system size dependence is studied by comparing the resulting intermittency index for heavy ion collisions of different nuclei at beam energies of $40A$, $80A$ and $150A$ GeV. The resulting intermittency index from our simulations is similar to the reported values of the NA61 collaboration, if nuclear interactions are included. The observed apparent intermittency signal is the result of the correlated proton pairs with small relative transverse momentum $\Delta p_{t}$, which would be enhanced by hadronic potentials, and this correlation between the protons is slightly influenced by the coalescence parameters and the relative invariant four-momentum $q_{inv}$ cut.