Physical Review Letters, cilt.136, sa.8, 2026 (SCI-Expanded, Scopus)
The first observation of single top quark production in association with a (Formula presented) and a (Formula presented) 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 (Formula presented). 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 (Formula presented) production. The measured cross sections for (Formula presented) production are (Formula presented) and (Formula presented) for (Formula presented) 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.