Search for $WW/WZ$ resonance production in $\ell \nu qq$ final states in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

A search is presented for new resonances decaying to a $WW$ or $WZ$ boson pair, where one $W$ boson decays leptonically and the other $W$ or $Z$ boson decays hadronically. It is based on proton-proton collision data, utilizing 36.1 fb$^{-1}$, collected with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of $\sqrt{s}$ = 13 TeV in 2015 and 2016. The search is sensitive to diboson resonance production via quark-antiquark, gluon-gluon and vector-boson fusion mechanisms. No significant excess is observed in data with respect to Standard Model backgrounds. Several benchmark models are used to interpret the results. Limits on the production cross section are set for a new narrow scalar resonance, a new heavy vector-boson coupling to the Standard Model gauge bosons and a spin-2 Randall-Sundrum bulk graviton.