Bottomonium studies at LHC energy using ALICE muon spectrometer

The bottomonium (Υ), is a useful probe to investigate the properties of the deconfined medium, created in ultra-relativistic heavy-ion collisions. The medication of Υ production at LHC energies in heavy-ion collisions with respect to the binary-scaled yield in pp collisions has been explained by color screening mechanisms. In the bottomonium sector, the regeneration effects are expected to be negligible due to the small number of b quarks produced in relativistic heavy-ion collisions. However, the Cold Nuclear Matter (CNM) effects which include shadowing, parton energy loss, interaction with hadronic medium may also lead to a modification of bottomonium production. In order to disentangle the CNM effects from the hot nuclear matter effects, Υ production has been studied in p-Pb collisions in which the QGP is not expected to be formed. I have studied the bottomonium production via di-muon decay channel in pp, p-Pb and Pb-Pb collisions using the ALICE Muon Spectrometer. The inclusive Υ (nS) production cross sections have been measured at forward rapidity (2.5 < y < 4) in pp collisions at √s = 5.02 TeV. The energy dependency of Υ (nS) states has been evaluated and a steady increase of the cross-sections is observed with increasing √s. The differential cross sections have been compared with ICEM and CEM model calculation. A good agreement within the uncertainties has been observed between the experimental results and model calculations. The measurements of the rapidity, transverse momentum and centrality dependence of the Υ(1S) nuclear modification factor in p-Pb collisions at √s NN = 8.16 TeV have been reported. The results show a suppression of the Υ(1S) yields, with respect to the ones measured in pp collisions at the same center-of-mass energy. The R_pPb values are similar at forward and backward rapidity with a slightly stronger suppression at low p_T , while in both rapidity intervals there is no evidence for a centrality dependence of the Υ(1S) Q pPb . Models based on nuclear shadowing, coherent parton energy loss or interactions with comoving particles fairly describe the data at forward rapidity, while they tend to overestimate the RpPb at backward y cms . The Υ(2S) R pPb has also been measured, showing a strong suppression, similar to the one measured for the Υ(1S), in the two investigated rapidity intervals. Finally, a first measurement of the Υ(3S) has also been performed, even if the large uncertainties prevent a detailed comparison of its behaviour in p–Pb collisions with respect to the other bottomonium states. The measurements of Υ (1S) and Υ (2S) production at forward rapidity combining the 2015 and 2018 data sets are reported for Pb-Pb collision at √s NN = 5.02 TeV. The suppression of Υ (1S) gets stronger for the more central collisions. The rapidity dependence of Υ (1S) R PbPb hints to a decrease in the value at the most forward rapidity interval comparison to the central range of the ALICE measurement. No significant pT dependence of R_PbPb is observed up to 15 GeV/c. It is worth noting that the nuclear modification factor in p-Pb collision shows a significant p_T dependence in both forward and backward intervals measured by ALICE and LHCb. The difference in behavior between p-Pb and Pb-Pb collisions may impose some constraints on theoretical models in near future. The available theoretical calculations fail to describe the bottomonium production fully the rapidity dependence observed for the R PbPb of Υ (1S) in the ALICE forward region. The Υ (2S) state is found to have larger suppression (3 times) than the Υ (1S).