Sirunyan, A. M.Turnasyan, A.Adam, W.Arribrogi, F.Asilar, E.Bergauer, T.Brandstetter, J.2025-03-232025-03-2320170031-90071079-7114https://doi.org/10.1103/PhysRevLett.119.242001https://hdl.handle.net/11486/5536The 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 root(S)(NN) = 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 sigma(tt) = 45 +/- 8 nb, consistent with predictions from perturbative quantum chromodynamics.eninfo:eu-repo/semantics/openAccessBoson ProductionPpb CollisionsArticle1192410.1103/PhysRevLett.119.242001292867352-s2.0-85038597618Q1WOS:000417934800002Q1