Search for vector-boson resonances decaying to a top quark and bottom quark in the lepton plus jets final state in pp collisions at s=13 TeV with the ATLAS detector

A search for new charged massive gauge bosons, W^′, is performed with the ATLAS detector at the LHC. Data were collected in proton–proton collisions at a center-of-mass energy of s=13 TeV and correspond to an integrated luminosity of 36.1 fb⁻¹. This analysis searches for W^′ bosons in the W^′→tb¯ decay channel in final states with an electron or muon plus jets. The search covers resonance masses between 0.5 and 5.0 TeV and considers right-handed W^′ bosons. No significant deviation from the Standard Model (SM) expectation is observed and upper limits are set on the W^′→tb¯ cross section times branching ratio and the W^′ boson effective couplings as a function of the W^′ boson mass. For right-handed W^′ bosons with coupling to the SM particles equal to the SM weak coupling constant, masses below 3.15 TeV are excluded at the 95% confidence level. This search is also combined with a previously published ATLAS result for W^′→tb¯ in the fully hadronic final state. Using the combined searches, right-handed W^′ bosons with masses below 3.25 TeV are excluded at the 95% confidence level.