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

Pengcheng Li,Yongjia Wang,Jan Steinheimer,Qingfeng Li,Hongfei Zhang

doi:10.1016/j.physletb.2021.136393

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 Δpt, 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 qinv cut.

Highlights

The exploration of the properties of the Quark Gluon Plasma (QGP) [1–3] and the phase structure of quantum chromodynamics (QCD) [4] are the main objectives in relativistic heavy-ion collisions (HICs)
The observed apparent intermittency signal is the result of the correlated proton pairs with small relative transverse momentum ∆pt, 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 qinv cut
In the following we will show the results of the proton intermittency analysis for 40Ar+45Sc, 131Xe+139La collisions with centralities 0-5%, 5-10% and 10-15% and central 197Au+197Au collisions (0-10%) (the centrality is defined by impact parameter distribution c = (b/bmax)2 of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model)

Summary

Introduction

The exploration of the properties of the Quark Gluon Plasma (QGP) [1–3] and the phase structure of quantum chromodynamics (QCD) [4] are the main objectives in relativistic heavy-ion collisions (HICs). Various theoretical investigations suggest that at finite baryon chemical potential and temperature, there could be a critical end point (CEP) in the QCD phase diagram [8–11]. In order to explore the QCD phase diagram at finite net-baryon density, one tries to vary the temperature and baryon chemical potential of the nuclear matter created in HICs by changing the colliding energy and size of the colliding nuclei as well as the centrality, leading to different freeze-out conditions in μB and T [12–14]. The analysis of local power-law fluctuations of the net-baryon density [27, 28] has drawn much attention. It can be detected through the measurement of the scaled factorial moments (SFMs) in transverse momentum space within the framework of a proton intermittency analysis [29–32]. A non-trivial intermittency effect was shown in a preliminary analysis of 40Ar+45Sc collisions at 150A GeV/c [35, 36]

Methods

Results

Conclusion