Measurement of inclusive and differential cross sections for W^+W^- production in proton-proton collisions at s = 13. 6 TeV

Measurements at s = 13. 6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34. 8 fb^-1. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavour and charge of the leptons, the number of jets, and number of jets originating from b quarks. The overall sensitivity is significantly better than that of previous results with a similar integrated luminosity. The improvements comes from a more refined control of experimental uncertainties and an improved fit strategy. An inclusive W^+W^- production cross section of 125. 7 5. 6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For first time in proton-proton collisions, WW events with zero, one, and at least two reconstructed jets are studied simultaneously and compared with recent theoretical predictions.