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

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.