Upsilon Productions at STAR

TL;DR

This paper reports measurements of the combined $
$ upsilon states' production cross section in proton-proton and deuteron-gold collisions at 200 GeV, comparing results with theoretical models and providing a benchmark for future heavy-ion studies.

Contribution

It presents the first measurements of $
$ upsilon production at RHIC energies in $p+p$ and d$+Au$ collisions, testing theoretical models and nuclear effects.

Findings

Measured cross section consistent with world data and CEM in $p+p$

Observed agreement with CEM and binary scaling in d$+Au$

Results serve as a baseline for future $
$ upsilon studies in heavy-ion collisions

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.