Measurement of the W boson decay branching fraction ratio B(W→cq)/B(W→qq¯′) in proton-proton collisions at s=13TeV

The most precise measurement to date of the Image 1 boson hadronic decay branching fraction ratio Image 2 is presented. The measurement is based on a sample of proton-proton collision data from the CERN LHC collected by the CMS experiment at a center-of-mass energy of 13 TeV in 2016–2018 with an integrated luminosity of 138fb−1. The large cross section of top quark-antiquark production at the LHC offers a sizable high-purity sample of Image 3 bosons suitable for this measurement. Events with one charged lepton (electron or muon) and at least four jets, two tagged as bottom quark jets, are analyzed. Charm jets are tagged using the presence of a muon inside the jet. The result, Image 4, is consistent with the standard model prediction and is twice as precise as the current world-average value.