Observation of top quark production in proton-nucleus collisions

The 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 t¯t signal against the background-only hypothesis is above 5 standard deviations. The measured cross section is σt¯t=45±8  nb, consistent with predictions from perturbative quantum chromodynamics.