Quarkonium Production at STAR

TL;DR

This paper reports on heavy quarkonium production measurements at RHIC, including spectra, nuclear modification factors, and elliptic flow, revealing suppression patterns in central collisions and contributions from B-meson feed-down.

Contribution

It provides new detailed measurements of J/psi and Upsilon production, including B-meson feed-down contributions and elliptic flow, at RHIC energies.

Findings

High-p_T J/psi suppression in central collisions

B-meson feed-down contributes 10-25% to J/psi yield

Elliptic flow of J/psi is consistent with zero

Abstract

We report the results on heavy quarkonium production in p+p and Au+Au collisions at midrapidity via the dielectron decay channel at sqrt(s_NN) = 200 GeV from the STAR experiment at RHIC. Results on the J/psi p_T spectra in p+p collisions are presented for 2 < p_T < 10 GeV/c. The B-meson feed-down contribution to the inclusive J/psi yield has been obtained using the J/psi-hadron azimuthal angular correlation in p+p collisions, and is found to be 10-25% in the range 4 < p_T < 12 GeV/c. The p_T spectrum and nuclear modification factor for J/psi with p_T < 10 GeV/c is reported, along with results from Upsilon(1S+2S+3S) production in Au+Au collisions. The nuclear modification factor for high-p_T J/psi (p_T > 5 GeV/c) is found to be consistent with unity in peripheral collisions, while a significant suppression of low-p_T J/psi and Upsilon is observed in central collisions. The elliptic flow of J/psi is reported for 20-60% central Au+Au collisions, and is found to be consistent with zero.