Measuring the Upsilon Nuclear Modification Factor at STAR

Suppression of quarkonia in heavy ion collisions with respect to proton-proton collisions due to the Debye screening of the potential between the heavy quarks was hypothesized to be a signature of the Quark Gluon Plasma (QGP). However, other effects besides Debye screening, such as the statistical recombination of quark anti-quark heavy flavor pairs, or co-mover absorption can also affect quarkonia production in heavy ion collisions. Quantifying the suppression of an entire family of quarkonium mesons can give us a model dependent constraint on the temperature. The suppression of Upsilon can be quantified by calculating the Nuclear Modification factor, RAA, which is the ratio of the production in Au+Au collisions to the production in p+p scaled by the number of binary collisions. We present our results for mid-rapidity Upsilon(1S+2S+3S) production in p+p and Au+Au collisions at sqrt(sNN) = 200 GeV. The centrality dependence of RAA will be shown for the combined Upsilon(1S+2S+3S) yield.

screening: Debye
heavy ion: scattering
quarkonium: production
potential: screening
quark gluon: plasma
suppression
heavy quark
quark antiquark
recombination
absorption