Intermittency analysis of proton numbers in heavy-ion collisions at energies available at the BNL Relativistic Heavy Ion Collider

TL;DR

This paper investigates fluctuations in proton numbers in heavy-ion collisions at various energies to identify signs of the QCD critical point, proposing methods to correct for background and detection efficiency effects.

Contribution

It introduces a cumulative variable method for background removal and a cell-by-cell efficiency correction technique for analyzing intermittency signals.

Findings

Systematic study of second-order SFMs across collision energies.

Development of background subtraction and efficiency correction methods.

Guidance for experimental search of the QCD critical point.

Abstract

Local density fluctuations near the QCD critical point has been suggested to exhibit a power-law behavior which can be probed by an intermittency analysis on scaled factorial moment (SFM) in relativistic heavy-ion collisions. The collision energy and centrality dependence of the second-order SFMs are systematically investigated in Au $+$ Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV within the UrQMD model. We estimate the noncritical background in the measurement of intermittency and propose a cumulative variable method to effectively remove the background contributions. We further study the effect of particle detection efficiency by implementing the RHIC (STAR) experimental tracking efficiencies in the UrQMD events. A cell-by-cell method is proposed for experimental application of efficiency corrections on SFM. This work can provide a guidance of background subtraction and efficiency correction for the experimental measurement of intermittency in the search of the QCD critical point in heavy-ion collisions.