Jet substructure and the search for neutral spin-one resonances in electroweak boson channels

Abstract

Strongly coupled models at the TeV scale often predict one or more neutral spin-one resonances (Z′) which have appreciable branching fractions to electroweak bosons, namely the Higgs and longitudinal W and Z. These resonances are usually believed to have multi-TeV mass due to electroweak precision constraints, placing them on the edge of LHC discovery reach. Searching for them is made particularly challenging because hadronically decaying electroweak bosons produced at such high energy will appear very similar to QCD jets. In this work we revisit the possibility of discovering these resonances at the LHC, taking advantage of recently developed jet substructure techniques. We make a systematic investigation of substructure performance for the identification of highly Lorentz-boosted electroweak bosons, which should also be applicable to more general new physics searches. We then estimate the model-independent Z′ discovery reach for the most promising final-state channels, and find significant improvements compared to previous analyses. For modes involving the Higgs, we focus on a light Higgs decaying to $b\bar{b}$. We further highlight several other novelties of these searches. In the case that vertex-based b-tagging becomes inefficient at high p _T , we explore the utility of a muon-based b-tag, or no b-tag at all. We also introduce the mode $Z^{\prime} \to Zh \to \left( {\nu \bar{\nu }} \right)\left( {b\bar{b}} \right)$ as a competitive discovery channel.