Midrapidity Antiproton-to-Proton Ratio from $A u + A u$ Collisions at $\sqrt{s_{NN}} = 130 GeV$

We report results on the ratio of midrapidity antiproton-to-proton yields in

Au + Au

collisions at

\sqrt{s_{NN}} = 130 GeV

per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of

| y | < 0.5

and

0.4 < p_{t} < 1.0 GeV / c

, the ratio is essentially independent of either transverse momentum or rapidity, with an average of

0.65 \pm {0.01}_{(stat)} \pm {0.07}_{(syst)}

for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the

p - \bar{p}

pair production becomes important at midrapidity, a significant excess of baryons over antibaryons is still present.

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Midrapidity Antiproton-to-Proton Ratio fromAu+AuCollisions atsNN=130GeV