Search for heavy resonances decaying into a W or Z boson and a Higgs boson in final states with leptons and b-jets in 36 fb^-1 of √s̅ = 13 TeV pp collisions with the ATLAS detector

A search is conducted for new resonances decaying into a W or Z boson and a 125 GeV Higgs boson in the νν¯bb,, ℓ^±νbb¯, and ℓ⁺ℓ−bb¯ final states, where ℓ^± = e^± or μ^±, in pp collisions at √s=13 TeV. The data used correspond to a total integrated luminosity of 36.1 fb⁻¹ collected with the ATLAS detector at the Large Hadron Collider during the 2015 and 2016 data-taking periods. The search is conducted by examining the reconstructed invariant or transverse mass distributions of W h and Zh candidates for evidence of a localised excess in the mass range of 220 GeV up to 5 TeV. No significant excess is observed and the results are interpreted in terms of constraints on the production cross-section times branching fraction of heavy W′ and Z′ resonances in heavy-vector-triplet models and the CP-odd scalar boson A in two-Higgs-doublet models. Upper limits are placed at the 95% confidence level and range between 9.0 × 10⁻⁴ pb and 7.3 × 10⁻¹ pb depending on the model and mass of the resonance.