CMS collaboration (2254 authors)Nayak, ArunaBargassa, PedrameBeirão Da Cruz E Silva, CristóvãoDi Francesco, AgostinoFaccioli, PietroGalinhas, BrunoGallinaro, MicheleHollar, JonathanLeonardo, NunoLloret Iglesias, LaraSeixas, JoaoStrong, GilesToldaiev, OleksiiVadruccio, DanieleVarela, JoaoVischia, PietroDavid Tinoco Mendes, AndreSilva, PedroMusella, Pasquale2019-02-052019-02-052017-12-14http://dx.doi.org/10.1103/PhysRevLett.119.242001http://hdl.handle.net/10400.26/27452The first observation of top quark production in proton-nucleus collisions is reported using proton-lead data collected by the CMS experiment at the CERN LHC at a nucleon-nucleon center-of-mass energy of sNN=8.16  TeV. The measurement is performed using events with exactly one isolated electron or muon candidate and at least four jets. The data sample corresponds to an integrated luminosity of 174  nb-1. The significance of the tt¯ signal against the background-only hypothesis is above 5 standard deviations. The measured cross section is σtt¯=45±8  nb, consistent with predictions from perturbative quantum chromodynamics.engjournal article2019-02-05