A search is conducted for a new vector resonance, called the W′, decaying into a W boson and a 125 GeV Higgs boson with a final state of lvbb, where l can be an electron or muon. The data were collected via pp collisions produced by the Large Hadron Collider running at √s = 13 TeV and recorded by the ATLAS detector. This data has a total integrated luminosity of 36.1 1/fb. The search is performed by examining the reconstructed invariant mass distributions of the WH candidates for evidence of localized excesses in the mass range 500 GeV to 5 TeV. No significant excess over the background prediction is observed and the results are interpreted in terms of constraints on the production cross-section times branching-fraction of a heavy W′ resonance. Upper limits are placed on the cross-section times branching-fraction at the 95% confidence level and range between 1 × 10−3 pb and 3 × 10−1 pb depending on the mass of the resonance. In addition, several statistical combinations are performed with searches for a W′ or Z′ using bosonic decay modes with final states qqqq, ννqq, lνqq, lνlν, llνν, llνl, llll, and qqbb, as well as leptonic decay modes with final states lν and ll. No significant deviation from the Standard-Model predictions is observed and upper limits on the cross-section are evaluated for a range of increasingly model dependent combinations of search results. These limits are also expressed in terms of constraints on the couplings of a heavy vector resonance to quarks, leptons, and bosons.
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