Deviation from quark-number scaling of the anisotropy parameter v_2 of pions, kaons, and protons in Au+Au collisions at sqrt(s_NN) = 200 GeV

TL;DR

This study measures the anisotropy parameter v_2 of identified hadrons in Au+Au collisions at 200 GeV, revealing deviations from quark-number scaling in noncentral collisions at high transverse kinetic energy.

Contribution

It provides the first detailed analysis of v_2 scaling behavior across different centralities and identifies deviations from quark-number scaling at high KE_T/n_q in noncentral collisions.

Findings

Quark-number scaling holds in central collisions (0-10%).

Deviations from scaling are observed at high KE_T/n_q in noncentral collisions (20-60%).

v_2 measurements extend up to p_T = 6 GeV/c for pions and protons.

Abstract

Measurements of the anisotropy parameter v_2 of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum p_T, and transverse kinetic energy KE_T at midrapidity (|\eta|<0.35) in Au+Au collisions at sqrt(s_NN) = 200 GeV are presented. Pions and protons are identified up to p_T = 6 GeV/c, and kaons up to p_T = 4 GeV/c, by combining information from time-of-flight and aerogel Cherenkov detectors in the PHENIX Experiment. The scaling of v_2 with the number of valence quarks (n_q) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KE_T/n_q in noncentral Au+Au collisions (20--60%), but this scaling remains valid in central collisions (0--10%).