Detecting a Boosted Diboson Resonance

New light scalar particles in the mass range of hundreds of GeV, decaying into a pair of W/Z bosons can appear in several extensions of the SM. The focus of collider studies for such a scalar is often on its direct production, where the scalar is typically only mildly boosted. The observed W/Z are therefore well-separated, allowing analyses for the scalar resonance in a standard fashion as a low-mass diboson resonance. In this work we instead focus on the scenario where the direct production of the scalar is suppressed, and it is rather produced via the decay of a significantly heavier (a few TeV mass) new particle, in conjunction with SM particles. Such a process results in the scalar being highly boosted, rendering the W/Z’s from its decay merged. The final state in such a decay is a “fat” jet, which can be either four pronged (for fully hadronic W/Z decays), or may be like a W/Z jet, but with leptons buried inside (if one of the W/Z decays leptonically). In addition, this fat jet has a jet mass that can be quite different from that of the W/Z/Higgs/top quark-induced jet, and may be missed by existing searches. In this work, we develop dedicated algorithms for tagging such multi-layered “boosted dibosons” at the LHC. As a concrete application, we discuss an extension of the standard warped extra dimensional framework where such a light scalar can arise. We demonstrate that the use of these algorithms gives sensitivity in mass ranges that are otherwise poorly constrained.