Rapidity and centrality dependence of proton and antiproton production from ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions at $\sqrt{S_{NN}}=130\mathrm{GeV}$

We report on the rapidity and centrality dependence of proton and antiproton transverse mass distributions from ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=130\mathrm{GeV}$ as measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Our results are from the rapidity and transverse momentum range of $\mid y\mid <0.5$ and $0.35<p_t<1.00\mathrm{GeV}∕c$. For both protons and antiprotons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within $\mid y\mid <0.5$. Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton (antiproton) yields and transverse mass distributions the possibility of prehadronic collective expansion may have to be taken into account.

Figure 1

(Color online) Midrapidity ($\mid y\mid ⩽0.5$) proton (left column) and antiproton (right column) transverse mass distributions for most peripheral (bottom) to most central (top) collisions. The definitions of the centrality bins are listed in Table 1. Relatively large systematic errors for protons in the low $m_t$ region are due to the background subtraction. Results from model fits are shown as dashed lines.

Figure 2

The rapidity distributions of (a) protons and (b) antiprotons and (c) the (average proton and antiproton) transverse momentum $⟨p_t⟩$, for most peripheral (bottom) to most central (top) collisions. The bin-to-bin systematic errors due to PID contamination were included in the plot. Overall systematic errors due to extrapolation into the $p_t$ range not covered by the experiment and the uncertainty in the track reconstruction efficiency are not shown in the figure.

Figure 3

(Color online) Midrapidity $⟨p_t⟩$ and $dN∕dy$ of protons and antiprotons as functions of the number of negatively charged hadrons. The corresponding number of participants are also shown at the top of the plots. Open symbols are fiducial yields and filled ones are integrated yields. Systematic errors are shown as shaded areas. Results from RQMD, RQMD with rescattering switched off (w/o) and HIJING are shown as solid lines, dashed lines, and dashed-dotted lines, respectively. The experimental data and the results from RQMD and HIJING include feeddown from hyperon decay.