Upsilon Production at the STAR Experiment with a Focus on New U+U Results

TL;DR

This paper reports measurements of Upsilon production across different collision systems at RHIC, revealing suppression patterns in heavy-ion collisions consistent with quark-gluon plasma formation and color screening effects.

Contribution

It provides new Upsilon production data in U+U collisions at 193 GeV, extending understanding of quarkonium suppression in heavy-ion environments.

Findings

Upsilon production in p+p collisions aligns with pQCD predictions.

Suppression observed in d+Au collisions exceeds model expectations.

Significant suppression in central Au+Au and U+U collisions supports quark-gluon plasma formation.

Abstract

We report recent Upsilon measurements in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV, and detail the analysis in U+U collisions at $\sqrt{s_{NN}}$=193 GeV. Results on Upsilon production versus rapidity are consistent with pQCD predictions in p+p collisions. However, Upsilon production in mid-rapidity (|y|<0.5) d+Au collisions is suppressed with respect to p+p collisions beyond model predictions that take into account modification of parton distribution functions and initial parton energy loss inside nuclei. The nuclear modification factor R_AA shows a significant suppression in central Au+Au and U+U collisions, consistent with model calculations including color screening effects in a deconfined medium.