Measurement of single top-quark production in association with a boson in collisions at √=13  TeV with the ATLAS detector

The inclusive cross section for the production of a single top quark in association with a boson is measured using 140 fb−1 of proton-proton collision data collected with the ATLAS detector at √=13 TeV. Events containing two charged leptons and at least one jet identified as originating from a -quark are selected. A multivariate discriminant is constructed to separate the ⁢ signal from the ⁢ ¯ background. The cross section is extracted using a profile likelihood fit to the signal and control regions and it is measured to be ⁢=7⁢5+15 −14 pb, in good agreement with the Standard Model prediction. The measured cross section is used to extract a value for the left-handed form factor at the ⁢⁢ vertex times the Cabibbo-Kobayashi-Maskawa matrix element |LV⁢⁢| of 0.97±0.10.