Energy Dependence of Moments of Net-Proton and Net-Charge Multiplicity Distributions at STAR

TL;DR

This study investigates how the moments of net-proton and net-charge distributions vary with collision energy in heavy-ion collisions, revealing significant deviations at certain energies that may indicate phase transition signatures.

Contribution

It extends the transverse momentum range for particle identification and analyzes the energy dependence of moments, highlighting notable structures in net-proton fluctuation measures.

Findings

Significant deviation of { ext{KV}} from unity below 39 GeV

Largest structure observed at 19.6 and 27 GeV

{ ext{KV}} approaches unity at energies above 39 GeV

Abstract

We present the energy dependence of moments of net-proton and net-charge multiplicity distributions in Au+Au collisions measured by the STAR experiment in the first phase of the Beam Energy Scan (BES) at the Relativistic Heavy Ion Collider (RHIC). By using the time of flight detector for particle identification, the upper transverse momentum ($p_{T}$) limit for proton and anti-proton is extended from 0.8 GeV/c up to 2 GeV/c. The $p_{T}$ and rapidity acceptance dependence study for the moments of net-proton distribution show that the larger the acceptance is, the greater the deviation from unity. The most pronounced structure is found in the energy dependence of {\KV} of net-proton distributions from the $0\sim5%$ most central collisions within $0.4<p_{T}<2$ GeV/c and at mid-rapidity $|y|<0.5$. At energies above 39 GeV, the values of {\KV} are close to unity and for energies below 39 GeV, it shows significant deviation below unity around 19.6 and 27 GeV, then a large increase above unity is observed at 7.7 GeV.