Measurement of Z$^0$-boson production at large rapidities in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV

The production of Z(0) bosons at large rapidities in Pb-Pb collisions at root s(NN) = 5.02 TeV is reported. Z(0) candidates are reconstructed in the dimuon decay channel (Z(0) -> mu(+) mu(-)), based on muons selected with pseudo-rapidity -4.0 < eta < -2.5 and p(T) > 20 GeV/c. The invariant yield and the nuclear modification factor, RAA, are presented as a function of rapidity and collision centrality. The value of R-AA for the 0-20% central Pb-Pb collisions is 0.67 +/- 0.11(stat.) +/- 0.03 (syst.) f 0.06(corr. syst.), exhibiting a deviation of 2.6 sigma from 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 2.3 sigma in the 0-90% centrality class and by 3 sigma in the 0-20% central collisions. (C) 2018 The Author(s). Published by Elsevier B.V.