Centrality Dependence of Charged Particle Multiplicity in Au-Au Collisions at sqrt(s_NN)=130 GeV

TL;DR

The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.

Abstract

We present results for the charged-particle multiplicity distribution at mid-rapidity in Au - Au collisions at sqrt(s_NN)=130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find $dN_{ch}/dη_{|η=0} = 622 \pm 1 (stat) \pm 41 (syst)$. The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.

Figures (4)

• Figure 1: Sketch of the geometry. For clarity, three PC3 sectors have been removed from the drawing.
• Figure 2: Tracks per event and per cm as a function of the distance to the event vertex.
• Figure 3: BBC vs. ZDC analog response (top panel) and minimum-bias multiplicity distribution in the PHENIX measurement aperture (lower panel). The lower axis converts the observed distribution to the corresponding average $dN_{ch}/d\eta$ for track multiplicities less than $\sim 120$; beyond that value the shape of the distribution has a significant contribution from fluctuations into the measurement aperture.
• Figure 4: Charged-particle pseudorapidity density per participant pair vs. the number of participants. Predictions from HIJING wang-gyulassy and EKRT ekrt models, and a simple phenomenological fit are also shown. The shaded area represents the systematic errors of $dN_{ch}/d\eta$ and $N_{p}$. The errors of $N_{c}$ are in Table 1.