Does quark number scaling breakdown in Pb+Pb collisions at Root_s = 2.76 TeV?

2012/07/08 by R. Lacey, Roy A. Lacey, Yi Gu +15
Mathematics · Physics and Astronomy · #High-Energy Particle Collisions Research #Quantum Chromodynamics and Particle Interactions #Stochastic processes and statistical mechanics #nucl-ex #nucl-th

paper · pdf · doi:10.48550/arxiv.1207.1886

4 pages, 4 figures. Submitted for publication (Typos corrected in this version)

arxiv created 2012/07/14 · arxiv updated 2012/07/17

Abstract

The anisotropy coefficient v₂, for unidentified and identified charged hadrons [pions (π), kaons (K) and protons (p)] measured in Au+Au collisions at √s_NN= 0.20 TeV (RHIC) and Pb+Pb collisions at √s_NN= 2.76 TeV (LHC), are compared for several collision centralities (cent) and particle transverse momenta p_T. In contrast to the measurements for charged hadrons, the comparisons indicate a sizable increase of v₂(p_T) for π,K and p, as well as a blueshift of proton v₂(p_T), from RHIC to LHC. When this blueshift is accounted for, the LHC data [for π, K, p] show excellent scaling of v₂(KE_T) with the number of valence quarks (n_q), for a broad range of transverse kinetic energies (KE_T) and collision centralities. These observations suggest a larger mean sound speed <c_s(T)> for the plasma created in LHC collisions, and significant radial flow generation after its hadronization.

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