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Charge Particle Multiplicity and Transverse Energy Measurements in Au-Au collisions in PHENIX at RHIC

A. Bazilevsky

TL;DR

The paper investigates how global observables $N_{ch}$ and $E_{T}$, measured at mid-rapidity in Au-Au collisions, reflect the initial conditions of high-energy nuclear interactions. Using a consistent PHENIX analysis at $sqrt{s_{_{NN}}}=200$ GeV and centrality defined by $N_p$, it presents $dE_{T}/d exteta$ and $dN_{ch}/d exteta$ measurements and compares them to several theoretical scenarios, including EKRT, HIJING, KLN, and minijet models. The results show a centrality-dependent rise in densities, a modest increase from 130 to 200 GeV in central collisions, and a near-constant mean $E_T$ per charged particle across centralities and energies, supporting gluon-saturation and mini-jet pictures while challenging some saturation and HIJING predictions. Across RHIC and fixed-target data, the densities exhibit a logarithmic rise with $ oot sqrt{s_{NN}}$, highlighting consistent global-variables behavior from SPS to RHIC energies with implications for initial-state dynamics and particle production mechanisms.

Abstract

We present results on charged particle and transverse energy densities measured at mid-rapidity in Au-Au collisions at sqrt(s_{NN})=200 GeV. The mean transverse energy per charged particle is derived. The results are presented as a function of centrality, which is defined by the number of participating nucleons, and compared to results obtained in Au-Au collisions at sqrt{s_{NN})=130 GeV. A comparison with calculations from various theoretical models is performed.

Charge Particle Multiplicity and Transverse Energy Measurements in Au-Au collisions in PHENIX at RHIC

TL;DR

The paper investigates how global observables and , measured at mid-rapidity in Au-Au collisions, reflect the initial conditions of high-energy nuclear interactions. Using a consistent PHENIX analysis at GeV and centrality defined by , it presents and measurements and compares them to several theoretical scenarios, including EKRT, HIJING, KLN, and minijet models. The results show a centrality-dependent rise in densities, a modest increase from 130 to 200 GeV in central collisions, and a near-constant mean per charged particle across centralities and energies, supporting gluon-saturation and mini-jet pictures while challenging some saturation and HIJING predictions. Across RHIC and fixed-target data, the densities exhibit a logarithmic rise with , highlighting consistent global-variables behavior from SPS to RHIC energies with implications for initial-state dynamics and particle production mechanisms.

Abstract

We present results on charged particle and transverse energy densities measured at mid-rapidity in Au-Au collisions at sqrt(s_{NN})=200 GeV. The mean transverse energy per charged particle is derived. The results are presented as a function of centrality, which is defined by the number of participating nucleons, and compared to results obtained in Au-Au collisions at sqrt{s_{NN})=130 GeV. A comparison with calculations from various theoretical models is performed.

Paper Structure

This paper contains 2 sections, 5 figures.

Table of Contents

  1. INTRODUCTION
  2. RESULTS

Figures (5)

  • Figure 1: $dE_{T}/d\eta$ (top panels) and $dN_{ch}/d\eta$ (bottom panels) per pair of participants versus $N_{p}$ measured at $\sqrt{s_{_{NN}}}=130$ GeV (left panels) and $\sqrt{s_{_{NN}}}=200$ GeV (right panels); The lines represent the effect of the $\pm1\sigma$ centrality-dependent systematic errors, the error bars are the total systematic errors.
  • Figure 2: $R_{200/130}$ for $dE_{T}/d\eta$ (top) and $dN_{ch}/d\eta$ (bottom) versus centrality; $N_{p}$ is taken from data at $\sqrt{s_{_{NN}}}=200$ GeV; for the explanation of error representation, see the caption of Fig. 1.
  • Figure 3: The comparison of $dN_{ch}/d\eta$ at $\sqrt{s_{_{NN}}}=130$ GeV and 200 GeV along with $R_{200/130}$ as a function of centrality to the following models: EKRT ekrt (solid line), HIJING hijing (dotted line), KLN kln (dashed line) and mini-jet minijet (shaded area).
  • Figure 4: $dE_{T}/dy|_{y=0}$ (left) and $dN_{ch}/dy|_{y=0}$ (right) per pair of participants versus $\sqrt{s_{_{NN}}}$ for the most central collisions. Data are taken from PHOBOS phobos, BRAHMS brahms, STAR star, WA97/NA57 wa97, WA98 wa98, NA49 na49, CERES ceres, E802 e802 and E814/E877 e814. The centrality is indicated in brackets.
  • Figure 5: $dE_{T}/d\eta|_{\eta=0}$ / $dN_{ch}/d\eta|_{\eta=0}$ versus $N_{p}$ (left) and $\sqrt{s_{_{NN}}}$ (right) for the most central collisions. SPS and AGS data are taken from WA98 wa98, NA49 na49 and E814/E877 e814.