CMS collaboration (2240 authors)Nayak, ArunaBargassa, PedrameBeirão Da Cruz E Silva, CristóvãoCalpas, BettyDi Francesco, AgostinoFaccioli, PietroFerreira Parracho, Pedro GuilhermeGallinaro, MicheleHollar, JonathanLeonardo, NunoLloret Iglesias, LaraRodrigues Antunes, JoaoSeixas, JoaoToldaiev, OleksiiVadruccio, DanieleVarela, JoaoVischia, PietroDavid Tinoco Mendes, AndreSilva, PedroMusella, PasqualePela, Joao2019-02-042019-02-042017-08-23http://dx.doi.org/10.1103/PhysRevLett.119.082301http://hdl.handle.net/10400.26/27281The production of jets in association with Z bosons, reconstructed via the μ+μ- and e+e- decay channels, is studied in pp and, for the first time, in Pb-Pb collisions. Both data samples were collected by the CMS experiment at the LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The Pb-Pb collisions were analyzed in the 0%–30% centrality range. The back-to-back azimuthal alignment was studied in both pp and Pb-Pb collisions for Z bosons with transverse momentum pTZ>60  GeV/c and a recoiling jet with pTjet>30  GeV/c. The pT imbalance xjZ=pTjet/pTZ, as well as the average number of jet partners per Z, RjZ, was studied in intervals of pTZ. The RjZ is found to be smaller in Pb-Pb than in pp collisions, which suggests that in Pb-Pb collisions a larger fraction of partons associated with the Z bosons fall below the 30  GeV/c pTjet threshold because they lose energy.engjournal article2019-02-04