Heavy Ion Tea

Upsilon production in p+p and Au+Au collisions at 200 GeV in STAR

Rosi Reed (UC Davis)

Abstract: Quarkonia is a good probe of the dense matter produced in heavy-ion collisions at RHIC because it is produced early in the collision and the production is theorized to be suppressed due to the Debye color screening of the potential between the heavy quarks.  A model dependent measurement of the temperature of the Quark Gluon Plasma (QGP) can be determined by examining the ratio of the production of various quarkonia states in heavy ion collisions versus p+p collisions because lattice calculations indicate that the quarkonia states will be sequentially suppressed.  Suppression is quantified by calculating ${R}_{AA}$, which is the ratio of the production in p+p scaled by the number of binary collisions to the production in Au+Au. The $\Upsilon$ states are of particular interest because at 200 GeV the effects of feed down and co-movers are smaller than for J/$\psi$, which decreases the systematic uncertainty of the ${R}_{AA} calculation. We will present our results for mid-rapidity $\Upsilon$ production in p+p, as well as our preliminary results in Au+Au at $\sqrt{{S}_{NN }}$ = 200 GeV. These results will then be compared with theoretical QCD calculations.