Measurements of J/ψ Production and Polarization in p+p and p+Au Collisions at s NN = 200 GeV with the STAR Experiment

Zhen Liu

doi:10.1142/s2010194518600157

Abstract

We present the measurements of [Formula: see text] production at mid-rapidity via the di-muon decay channel in p+p and p+Au collisions at [Formula: see text] = 200 GeV by the STAR experiment at RHIC. In p+p collisions, the measured inclusive [Formula: see text] cross section can be qualitatively described by model calculations. The [Formula: see text] polarization parameters, [Formula: see text], [Formula: see text] as well as the frame-invariant quantity [Formula: see text], are presented as a function of transverse momentum in both the helicity and Collins-Soper frames. No significant polarization is observed. In addition, the nuclear modification factor for inclusive J/[Formula: see text] in p+Au collisions is similar to that measured in d+Au collisions and favors an additional nuclear absorption effect on top of the nuclear PDF effect.

Highlights

Understanding J/ψ production mechanism in elementary collisions has been a longterm interest both experimentally and theoretically[1]
Measurements of the J/ψ cross section[3] and polarization, both of which are sensitive to the J/ψ production mechanism, can be used to distinguish among different models[4]
With the Muon Telescope Detector (MTD) di-muon trigger, the STAR recorded two data sets corresponding to integrated luminosities of 122 pb−1 for p+p collisions and 409 nb−1 for p+Au collisions at √sNN = 200 GeV during the RHIC 2015 run

Summary

Introduction

Understanding J/ψ production mechanism in elementary collisions has been a longterm interest both experimentally and theoretically[1]. Interpretation of the J/ψ suppression measured in heavy-ion collisions is still challenging due to the presence of other This is an Open Access article published by World Scientific Publishing Company. With the MTD di-muon trigger, the STAR recorded two data sets corresponding to integrated luminosities of 122 pb−1 for p+p collisions and 409 nb−1 for p+Au collisions at √sNN = 200 GeV during the RHIC 2015 run In these proceedings, we present: (i)√measurements of inclusive J/ψ cross section and polarization in p+p collisions at s = 200 GeV; and (ii) measurements of nuclear modification factor (RpAu) for inclusive J/ψ in p+Au collisions at √sNN = 200 GeV.

PHENIX Global uncertainty

Summary