Disentangling stopped proton and inclusive net-proton fluctuations at RHIC

TL;DR

This paper analyzes net-proton fluctuations at RHIC, disentangling stopped and produced proton contributions to better identify signals of the QCD critical point, revealing a pronounced non-monotonic behavior near 19.6 GeV.

Contribution

It introduces a method to separate stopped proton contributions from produced protons in net-proton fluctuation measurements at RHIC.

Findings

Non-monotonic behavior in net-proton fluctuations around 19.6 GeV is more pronounced after removing stopped proton contributions.

Disentangling stopped and produced proton fluctuations clarifies signals related to the QCD critical point.

The study enhances understanding of fluctuation sources in heavy-ion collision experiments.

Abstract

The recent results on net-proton and net-charge multiplicity fluctuations from the beam energy scan program at RHIC have drawn much attention to explore the critical point in the QCD phase diagram. Experimentally measured protons contain contribution from various processes such as secondaries from higher mass resonance decay, production process, and protons from the baryon stopping. Further, these contributions also fluctuate from event to event and can contaminate the dynamical fluctuations due to the critical point. We present the contribution of stopped proton and produced proton fluctuations in the net-proton multiplicity fluctuation in \auau collisions measured by STAR experiment at RHIC. The produced net-proton multiplicity fluctuations using cumulants and their ratios are studied as a function collision energies. After removing the stopped proton contribution from the inclusive proton multiplicity distribution, a non-monotonic behavior is even more pronounced in the net-proton fluctuations around \sqsn = 19.6 GeV, both in $S\sigma$ and $\kappa\sigma^2$. The present study will be useful to understand the fluctuations originating due to critical point.