engleski

Z-boson production in p-Pb collisions at √sNN = 8.16 and Pb-Pb collisions at √sNN = 5.02 TeV

Measurement of Z-boson production in p-Pb collisions at √sNN = 8.16 TeV and Pb-Pb collisions at √sNN = 5.02 TeV is reported. It is performed in the dimuon decay channel, through the detection of muons with pseudorapidity −4 < ηµ < −2.5 and transverse momentum pµT > 20 GeV/c in the laboratory frame. The invariant yield and nuclear modification factor are measured for opposite- sign dimuons with invariant mass 60 < mµµ < 120 GeV/c2 and rapidity 2.5 < yµµ cms < 4. They are presented as a function of rapidity and, for the Pb-Pb collisions, of centrality as well. The results are compared with theoretical calculations, both with and without nuclear modifications to the Parton Distribution Functions (PDFs). In p-Pb collisions the center-of-mass frame is boosted with respect to the laboratory frame, and the measurements cover the backward (−4.46 < yµµ cms < −2.96) and forward (2.03 < yµµ cms < 3.53) rapidity regions. For the pPb collisions, the results are consistent within experimental and theoretical uncertainties with calculations that include both free-nucleon and nuclear- modified PDFs. For the Pb-Pb collisions, a 3.4σ deviation is seen in the integrated yield between the data and calculations based on the free- nucleon PDFs, while good agreement is found once nuclear modifications are considered.

Z-boson production ; p-Pb collisions

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