A search for new diboson resonances in the boosted semi-leptonic final state at $\sqrt{s}=13$ TeV with the ATLAS detector

A search is presented for new resonances decaying to a pair of boosted Standard Model bosons, $WV$, where the $W$ boson decays leptonically ($W\rightarrow\ell\nu$, with $\ell=e,\mu$) and the other weak boson, $V$ ($V=W,Z$), decays hadronically ($V\rightarrow q\bar{q}'/q\bar{q}$, with $q,q'=u,d,c,s,b$). The data were collected with the ATLAS detector at the CERN Large Hadron Collider, during the 2015 and 2016 periods of $pp$ collisions, at a center-of-mass energy $\sqrt{s}=13\,$TeV, and correspond to a total integrated luminosity of $36.1\,$fb$^{-1}$. The hadronic decay of the boosted $V$ boson is reconstructed as a single large-radius jet, and the leptonic decay of the $W$ boson is reconstructed as a lepton and missing transverse energy. The search is sensitive to resonances produced with quark-antiquark fusion, gluon-gluon fusion, and vector-boson fusion. No significant excesses are observed above the Standard Model background prediction. Upper limits on production cross section times branching ratio to $WV$ are set at a 95 % confidence level for selected benchmark signal models. Models of a neutral, narrow scalar boson (spin-0), charged and neutral vector bosons (spin-1) coupling to the Standard Model gauge bosons, and a neutral Randall-Sundrum bulk graviton (spin-2) are considered. The search significantly improves the limits produced in recent searches.