Hayrapetyan, A.Makarenko, V.Tumasyan, A.Adam, W.Andrejkovic, J. W.Benato, L.Bergauer, T.2026-04-252026-04-2520260031-90071079-7114https://doi.org/10.1103/rk6w-1pclhttps://hdl.handle.net/11486/8429The first observation of single top quark production in association with a W and a Z boson in proton-proton collisions is reported. The analysis uses data at center-of-mass energies of 13 and 13.6 TeV recorded with the CMS detector at the CERN LHC, corresponding to a total integrated luminosity of 200 fb(-1). Events with three or four charged leptons, which can be electrons or muons, are selected. Advanced machine-learning algorithms and improved reconstruction methods, compared to an earlier analysis, result in an unprecedented sensitivity to tWZ production. The measured cross sections for tWZ production are 248 +/- 52 fb and 242 +/- 77 fb for root s = 13 and 13.6 TeV, respectively. The signal is established with a statistical significance of 5.8 standard deviations, with 3.5 expected, compared to the background-only hypothesis.eninfo:eu-repo/semantics/openAccessArticle136810.1103/rk6w-1pcl418249682-s2.0-105032038037Q1WOS:001716775000001Q10000-0003-1058-11630000-0003-2831-69820000-0002-3955-43990009-0008-1661-35370000-0001-6250-84650000-0002-2729-62730000-0003-1967-6783