Upsilon Productions at STAR

Abstract

The $\Upsilon(1S+2S+3S)\to e^{+}e^{-}$ cross section is measured at mid-rapidity ($y$) in $p+p$ collisions and in d$+Au$ collisions at center-of-mass energy $\sqrt{s}$ = 200 GeV with the STAR detector at RHIC. In $p+p$, the measured cross section is found to be consistent with the world data trend as a function of $\sqrt{s}$, in agreement with the Color Evaportaion Model (CEM), and underestimated by the Color Singlet Model (CSM) up to the Next-to-Leading-Order Quantum Chromodynamics (NLO QCD) calculations. In d+$Au$, the measured cross section is in agreement with the CEM prediction with anti-shadowing effects, and the nuclear modification factor indicates that $\Upsilon(1S+2S+3S)$ production follows binary scaling within the current uncertainties. These measurements provide a benchmark for the future measurements of $\Upsilon$ production in $Au+Au$ collisions.