Search for the QCD Critical Point by Higher Moments of Net-proton Multiplicity Distributions at STAR

TL;DR

This study measures higher moments of net-proton multiplicity distributions in heavy-ion collisions to search for the QCD critical point, analyzing their energy and centrality dependence and comparing with models and expectations.

Contribution

It provides new experimental data on higher moments of net-proton distributions across different energies and centralities, aiding the search for the QCD critical point.

Findings

Moment products show energy and centrality dependence.

Results are consistent with Poisson expectations in some regimes.

Comparison with models helps understand non-critical effects.

Abstract

We present the measurements of the higher moments of the net-proton multiplicity distributions for Au+Au collisions from the first phase of the beam energy scan program at RHIC. The measurements are carried out at midrapidity ($|y|<0.5$) and within the transverse momentum range $0.4<p_{T}<0.8$ {\gevc} by STAR. The moment products, $\KV$ and $\SD$, which are related to the ratios of various order baryon number susceptibilities and sensitive to the correlation length, are applied to search for the QCD critical point. We report the centrality and energy dependence of the moment products ({\KV} and {\SD}), results are compared with Poisson expectations. The experiment data are also compared with transport model calculation to understand the non-critical physics effects.