Search for W ′ → t b ¯ in the lepton plus jets final state in proton–proton collisions at a centre-of-mass energy of s = 8 TeV with the ATLAS detector

A search for new charged massive gauge bosons, called W^′, is performed with the ATLAS detector at the LHC, in proton–proton collisions at a centre-of-mass energy of s=8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb⁻¹. This analysis searches for W^′ bosons in the W^′→tb¯ decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W^′ bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W^′→tb¯ cross-section times branching ratio and on the W^′-boson effective couplings as a function of the W^′-boson mass using the CL_s procedure. For a left-handed (right-handed) W^′ boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.