Speaker
Description
The suppression of Upsilon-mesons in the hot quark-gluon medium (QGP) versus reduced feed-down is investigated in heavy-ion collisions at energies reached at RHIC and at LHC. 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 the main Y(2S) suppression is caused by hot-medium effects in the collectively expanding QGP. The importance of reduced feed-down increases with energy. The p_T-dependence is flat due to the relativistic Doppler effect. Possible suppression effects due to the transient electromagnetic fields in more peripheral collisions are shown to be negligible. The predicted Y(1S)-suppression in Pb-Pb at sqrt(s_NN) = 5.02 TeV is compared with CMS data. Cold nuclear matter effects are discussed for p-Pb at the same energy.
[1] J. Hoelck, F. Nendzig, and G. Wolschin, Phys. Rev. C 95, 024905 (2017).
[2] J. Hoelck and G. Wolschin, Eur. Phys. J. A, 53 (2017).
