Search for pair production of heavy particles decaying to a top quark and a gluon in the lepton+jets final state in proton-proton collisions at .

A search is presented for the pair production of new heavy resonances, each decaying into a top quark (t) or antiquark and a gluon (g). The analysis uses data recorded with the CMS detector from proton-proton collisions at a center-of-mass energy of 13 at the LHC, corresponding to an integrated luminosity of 138 . Events with one muon or electron, multiple jets, and missing transverse momentum are selected. After using a deep neural network to enrich the data sample with signal-like events, distributions in the scalar sum of the transverse momenta of all reconstructed objects are analyzed in the search for a signal. No significant deviations from the standard model prediction are found. Upper limits at 95% confidence level are set on the product of cross section and branching fraction squared for the pair production of excited top quarks in the decay channel. The upper limits range from 120 to 0.8 for a with spin-1/2 and from 15 to 1.0 for a with spin-3/2. These correspond to mass exclusion limits up to 1050 and 1700 for spin-1/2 and spin-3/2 particles, respectively. These are the most stringent limits to date on the existence of resonances.