Probing Heavy Neutral Higgs Bosons via Single Vector-Like Bottom Quark Production at the HL-LHC

TL;DR

This paper explores the potential to discover heavy neutral Higgs bosons through single vector-like bottom quark production at the HL-LHC, using advanced analysis techniques to improve detection sensitivity.

Contribution

It introduces a novel search strategy for heavy neutral Higgs bosons via vector-like bottom quark decays, employing machine learning to enhance discovery prospects.

Findings

Exotic decay channels can dominate over standard modes, with branching ratios up to 50%.

Multivariate analysis significantly extends the discovery reach compared to traditional methods.

Discovery potential reaches up to 1.6 TeV for the bottom quark mass with high luminosity.

Abstract

We investigate the discovery prospects of a singly produced vector-like bottom quark in the Type-II Two-Higgs-Doublet Model extended by an $SU(2)_L$ vector-like $(T,B)$ doublet. We focus on the non-standard decay chain $B \to \phi b$, followed by $\phi \to t\bar{t}$, where $\phi = H$ or $A$, leading to a final state with one charged lepton, missing transverse energy, and multiple $b$-jets. We perform a full simulation of both signal and Standard Model backgrounds at $\sqrt{s}=14$ TeV. We show that the exotic channels $B \to \phi b$ can dominate over the conventional decay modes, reaching branching ratios of order $50\%$ for both neutral scalars in the alignment limit. A conventional cut-based analysis provides a $5\sigma$ discovery significance only at sufficiently high integrated luminosity. By contrast, an XGBoost-based multivariate analysis substantially improves the signal-background discrimination and extends the discovery reach up to $m_B \simeq 1.3$ TeV with $600~\mathrm{fb}^{-1}$ and up to $m_B \simeq 1.6$ TeV with $3~\mathrm{ab}^{-1}$, even in the presence of systematic uncertainties as large as $15\%$.