Measurement of Z0-boson production at large rapidities in Pb–Pb collisions at √sNN=5.02 TeV

Abstract

The production of Z0bosons at large rapidities in Pb–Pb collisions at √sNN=5.02 TeVis reported. Z0candidates are reconstructed in the dimuon decay channel (Z0→μ+μ−), based on muons selected with pseudo-rapidity −4.0 <η<−2.5and pT>20GeV/c. The invariant yield and the nuclear modification factor, RAA, are presented as a function of rapidity and collision centrality. The value of RAAfor the 0–20% central Pb–Pb collisions is 0.67 ±0.11 (stat.)±0.03 (syst.)±0.06 (corr.syst.), exhibiting a deviation of 2.6σfrom unity. The results are well-described by calculations that include nuclear modifications of the parton distribution functions, while the predictions using vacuum PDFs deviate from data by 2.3σin the 0–90% centrality class and by 3σin the 0–20% central collisions.