Pseudorapidity distributions of charged particles from Au+Au collisions at the maximum RHIC energy, Sqrt(s_NN) = 200 GeV

TL;DR

Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around midrapidity, which constrain current models of particle production at the highest RHIC energy.

Abstract

We present charged particle densities as a function of pseudorapidity and collision centrality for the 197Au+197Au reaction at Sqrt{s_NN}=200 GeV. For the 5% most central events we obtain dN_ch/deta(eta=0) = 625 +/- 55 and N_ch(-4.7<= eta <= 4.7) = 4630+-370, i.e. 14% and 21% increases, respectively, relative to Sqrt{s_NN}=130 GeV collisions. Charged-particle production per pair of participant nucleons is found to increase from peripheral to central collisions around mid-rapidity. These results constrain current models of particle production at the highest RHIC energy.

Figures (5)

• Figure 1: Distributions of $dN_{ch}/d\eta$ for centrality ranges of, top to bottom, 0-5%, 5-10%, 10-20%, 20-30%, 30-40%, and 40-50%. The SiMA and BBC results are indicated by circles and triangles, respectively. Statistical errors are shown for all points where they are larger than the symbol size.
• Figure 2: Charged-particle multiplicities normalized to the number of participant nucleon pairs (see Table I) for the present 0-5% central (open circles) and 40-50% central (open squares) Au+Au results at $\sqrt{s_{NN}}$=200 GeV, the BRAHMS 0-5% Au+Au results bearden01a at $\sqrt{s_{NN}}$=130 GeV (closed circles) and the 9.4% central Pb+Pb data at $\sqrt{s_{NN}}$=17 GeV(closed triangles) of ref deines00. Data are plotted as a function of the pseudorapidity shifted by the relevant beam rapidity. Representative total uncertainties are shown for a few Au+Au points.
• Figure 3: (a-d) Measured $dN_{ch}/d\eta$ distributions for centrality ranges of 0-5%, 5-10%, 20-30% and 40-50%. Theoretical predictions by Kharzeev and Levin (solid line) and by the AMPT model (dashed line) are also shown. Result from $p\bar{p}$ collisions at $\sqrt{s}$=200 GeV Alner86, scaled by the Au+Au values of $\langle N_{part}\rangle/2$, are shown with stars (a,d).
• Figure 4: Ratio of $dN_{ch}/d\eta$ values at $\sqrt{s_{NN}}$=200 GeV and 130 GeV compared to the model calculations (see Fig. 3 caption). Total uncertainties are shown, assuming a 3% relative scaling uncertainty between the two energies.
• Figure 5: $dN_{ch}/d\eta$ per participant nucleon pair as a function of the average number of participants (see table) for $\eta$= 0 (circles), 3.0 (squares) and 4.5 (triangles). The curves show the model predictions (see Fig. 3 caption). The star denotes the $p\bar{p}$ result at $\eta=0$Alner86.