Centrality evolution of $p_t$ and $y_t$ spectra from Au-Au collisions at $\sqrt{s_{NN}}=200$ GeV

Abstract

A two-component analysis of spectra to $p_t=12$ GeV/c for identified pions and protons from 200 GeV Au-Au collisions is presented. The method is similar to an analysis of the $n_{ch}$ dependence of $p_t$ spectra from p-p collisions at 200 GeV, but applied to Au-Au centrality dependence. The soft-component reference is a Lévy distribution on transverse mass $m_t$. The hard-component reference is a Gaussian on $y_t$ with exponential ($p_t$ power-law) tail. Deviations of data from the reference are described by hard-component ratio $r_{AA}$ which generalizes nuclear modification factor $R_{AA}$. The analysis suggests that centrality evolution of pion and proton spectra is dominated by changes in parton fragmentation. The structure of $r_{AA}$ suggests that parton energy loss produces a negative boost $\Delta y_t$ of a large fraction (but not all) of the minimum-bias fragment distribution, and that lower-energy partons suffer relatively less energy loss, possibly due to color screening. The analysis also suggests that the anomalous $p/\pi$ ratio may be due to differences in the parton energy-loss process experienced by the two hadron species. This analysis provides no evidence for radial flow.

21 pages, 18 figures

References in corpus (3)

• Testing the theory of QGP-induced energy loss at RHIC and the LHC
• The multiplicity dependence of inclusive $p_t$ spectra from p-p collisions at $\sqrt{s}$ = 200 GeV
• Extrapolating parton fragmentation to low $Q^2$ in $e^{+}$-$e^{-}$ collisions

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• Ensemble mean ${\mathbf{p}}_{\mathbf{t}}$ vs charged-hadron multiplicities in high energy nuclear collisions
• Minimizing statistical and systematic bias in transverse momentum correlations for relativistic heavy-ion collisions
• QCD prediction of jet structure in 2D trigger-associated momentum correlations and implications for multiple parton interactions
• QGP droplet formation in small asymmetric collision systems