Susceptibilities and fluctuations in a Quark-Hadron System with Dynamical Recombination

TL;DR

This study uses a dynamical recombination model to analyze fluctuations and susceptibilities in a quark-hadron system across various energies, finding that hadronization processes obscure early QGP signals in final state measurements.

Contribution

It demonstrates that the dynamical recombination approach explains the disappearance of QGP fluctuation signals, aligning final state results with hadronic expectations across a wide energy range.

Findings

Final state calculations match hadronic results at all energies.

Recombination-like hadronization erases early QGP correlations.

No observable QGP fluctuation signals in final measurements.

Abstract

Within the framework of the dynamical recombination approach implemented in the partonic/hadronic quark Molecular Dynamics (qMD) model, we investigate numerous QGP signals constructed from the correlations and fluctuations of conserved charges, namely charged particle ratio fluctuations, charge transfer fluctuations as well as various ratios of susceptibilities. We argue that more generally, the covariances and the variances of the conserved charges divided by the number of charged particles are a measure of the quark number susceptibilities and are thus sensitive to the phase of the system. Computations carried within samples of central qMD events from low AGS energies on ($E_{lab}=2$ AGeV) up to the highest RHIC energies available ($\sqrt{s_{NN}}=200$ GeV) show that the final state calculations are always compatible with the hadronic result. From analyses performed as a function of time with our sample of events at $\sqrt{s_{NN}}=200$ GeV, we find the recombination-like hadronization process the qMD system undergoes to be responsible for the vanishing of the early stage QGP correlations and fluctuations. These results might explain the compatibility of the measurements on charged particle ratio fluctuations with the hadronic expectations and leave no room for the experimental observation of any QGP fluctuation/correlation signals based upon the susceptibilities of the conserved charges.