Search for the tWZ process in the boosted region with the CMS experiment

Searching for rare processes is a fundamental instrument in testing our understanding of the universe. The high luminosity of proton-proton collisions delivered by the LHC in the 2016-2018 period (Run 2) allows us to search for processes with cross sections in the order of magnitude of 100 fb, such as the associated production of a single top quark with a W and a Z boson (tWZ). The tWZ process has never been observed and has been shown to be promisingly sensitive to new physics in the context of SM Effective Field Theory (SMEFT), especially in the high-pT spectrum of the final state products. An ongoing search for tWZ in the boosted top quark regime is presented. The data has been collected by the CMS experiment during LHC Run 2 and amounts to 138 fb−1. Final states with three leptons are explored, where the Z boson decays to two oppositely charged leptons, either the W boson or the top quark decays leptonically, the remaining one decays hadronically. A boosted leptonic top tagger was developed using a deep neural network to identify leptons and b-jets arising from the decay of a top quark. The tagger was validated in a phase space pure in events of top quark-antiquark pair production, with both tops decaying into leptons. The results are included in an inclusive tWZ search