Leptonic cascade decays of a heavy Higgs boson through vectorlike leptons at the LHC

TL;DR

This paper explores leptonic cascade decays of a heavy Higgs boson via vectorlike leptons at the LHC, providing model-independent bounds and future prospects for detecting new particles up to several TeV.

Contribution

It introduces a novel analysis of leptonic cascade decays for heavy Higgs and vectorlike leptons, applying existing LHC data to set bounds and project future sensitivities.

Findings

Current data constrains heavy Higgs and leptons up to 2 TeV and 1.5 TeV.

Future HL-LHC sensitivity extends reach to 2.7 TeV and 2 TeV.

Analysis applies broadly to new physics scenarios with similar final states.

Abstract

We demonstrate the potential of fully leptonic cascade decays of a heavy neutral Higgs boson through vectorlike leptons as a simultaneous probe for extended Higgs sectors and extra matter particles at the LHC. The processes we explore are unique in that their event topologies lead to di-boson-like leptonic final states with a lepton pair which does not reconstruct the mass of a gauge boson. By recasting existing $2\ell + E_T^{\rm miss}$ and $3/4\ell$ searches channels using run2 data from the LHC we obtain $\textit{model independent}$ bounds on the masses of heavy scalars and vectorlike leptons and use these results to explore future prospects at the HL-LHC. Our results can be directly applied to any kind of new physics scenarios sharing the final states and the event topology. For concreteness, we apply our results to a benchmark scenario: a two Higgs doublet model type-II augmented with vectorlike leptons. Remarkably, even with current data the sensitivity of our analysis shows a reach for masses of a heavy neutral Higgs and vectorlike leptons up to 2 TeV and 1.5 TeV, respectively. Even for low $\tan\beta \gtrsim 1,$ the analysis retains sensitivity to heavy Higgs masses slightly above 1 TeV. The future sensitivities at the HL-LHC extend the reach for heavy Higgses and new leptons to 2.7 TeV and 2 TeV, respectively.