In-Medium Y-Suppression and Feed-down in UU and PbPb Collisions

Abstract

The suppression of Y mesons in the hot quark-gluon medium (QGP) versus reduced feed-down is investigated in UU collisions at RHIC energies and PbPb collisions at LHC energies. Our centrality- and p_T-dependent model encompasses screening, collisional damping and gluodissociation in the QGP. For Y(1S) it is in agreement with both STAR and CMS data provided the relativistic Doppler effect and the reduced feed-down from the Y(nS) and chi_b(nP) states are properly considered. At both energies, most of the Y(1S) suppression is found to be due to reduced feed-down, whereas most of the Y(2S) suppression is caused by the hot-medium effects. The role of the latter increases with energy. The p_T-dependence is flat due to the relativistic Doppler effect and reduced feed-down. We predict the Y(1S)-suppression in PbPb at sqrt(s_NN) = 5.02 TeV.