Ratios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV

TL;DR

This study measures antiparticle-to-particle ratios for charged pions, kaons, and protons near mid-rapidity in central gold-gold collisions at 130 GeV, revealing a low baryo-chemical potential indicative of a high-energy nuclear environment.

Contribution

It provides new measurements of antiparticle-to-particle ratios at RHIC energies, estimating the baryo-chemical potential and comparing it to lower-energy collisions.

Findings

pbar/p ratio for protons is 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.)

Baryo-chemical potential mu_B is estimated at 45 MeV

The baryo-chemical potential is significantly lower than in lower-energy collisions.

Abstract

We have measured the ratios of antiparticles to particles for charged pions, kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) = 130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.