Snigirev, A.Sh,Hayrapetyan, A.Andrejkovic, J.W.Benato, L.Makarenko, V.Tumasyan, A.Adam, W.2026-04-212026-04-2120260031-90071079-711410.1103/rk6w-1pcl2-s2.0-105032038037https://hdl.handle.net/123456789/9074https://doi.org/10.1103/rk6w-1pclThe 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/openAccessArticle