Upsilon Suppression in PbPb Collisions at sqrt(s_NN) = 2.76 TeV
  We suggest that the combined effect of screening, gluon-induced dissociation, collisional damping, and reduced feed-down explains most of the sequential suppression of Y(nS) states that has been observed in PbPb relative to pp collisions at sqrt(s_NN) = 2.76 TeV. The suppression is thus a clear, albeit indirect, indication for the presence of a qgp. 
Felix Nendzig and Georg Wolschin
hep-ph nucl-th