PHENIX first measurement of the J/psi elliptic flow parameter v2 in Au+Au collisions at sqrt(sNN) = 200 GeV

TL;DR

This paper reports the first measurement of J/psi elliptic flow v2 in Au+Au collisions at 200 GeV, providing insights into J/psi production mechanisms and the role of recombination versus suppression.

Contribution

It presents the first measurement of J/psi v2 at both mid and forward rapidity in Au+Au collisions at RHIC, utilizing improved detector capabilities and larger data samples.

Findings

J/psi v2 measurements at different rapidities

Comparison with theoretical models of production mechanisms

Enhanced data precision over previous studies

Abstract

Recent results indicate that the J/psi suppression pattern differs with rapidity showing a larger suppression at forward rapidity. J/psi suppression mechanisms based on energy density (such as color screening, interaction with co-movers, etc.) predict the opposite trend. On the other hand, it is expected that more c\bar{c} pairs should be available to form quarkonia at mid-rapidity via recombination. Some models provide a way to differentiate J/psi production from initially produced c\bar{c} pairs and final state recombination of uncorrelated pairs, via the rapidity and transverse momentum dependence of the elliptic flow (v2). During 2007 data taking at RHIC, a large sample of Au+Au collisions at sqrt(sNN)=200 GeV was collected. The statistics has been increased compared to previous 2004 data set, thus allowing a more precise measurement of the J/psi production at both mid and forward rapidity. Furthermore, the PHENIX experiment benefited from the addition of a new detector, which improves the reaction plane resolution and allows us to measure the J/psi v2. Comparing this measurement to the positive D-mesons v2 (through non-photonic electron decays) will help constraining the J/psi production mechanisms and getting a more precise picture of the proportion of J/psi coming from direct production or charm quark coalescence. Details on how the J/psi v2 is measured at both rapidities are presented. The J/psi v2 as a function of transverse momentum are compared to existing models.