Measurement of the inclusive t t-bar cross section in final states with at least one lepton and additional jets with 302 pb−1 of pp collisions at sqrt(s) = 5.02 TeV

A measurement of the top quark pair (t ̄t) production cross section in proton proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default confguration, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identifed as originating from a b quark (b tagged). Events are classifed based on the number of all reconstructed jets and of b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is 62.5 ± 1.6 (stat)+2.6 −2.5 (syst) ± 1.2 (lumi) pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3±1.5 (stat)±2.4 (syst)±1.2 (lumi) pb, to be compared with the standard model prediction of 69.5 +3.5 −3.7 pb at next-to-next-to-leading order in perturbative quantum chromodynamics