Exotic Higgs Decay $h\rightarrow\phi\phi\rightarrow 4b$ at the LHeC

TL;DR

This paper investigates the potential of the LHeC to detect exotic Higgs decays into four b-quarks, showing it can significantly outperform the LHC in sensitivity, especially for light scalar masses.

Contribution

It introduces a novel analysis of Higgs exotic decay detection at the LHeC, demonstrating superior sensitivity compared to the LHC for the $h ightarrow ext{4b}$ channel.

Findings

LHeC can constrain the decay parameter $C_{4b}^2$ to a few percent with 100 fb$^{-1}$.

With 1 ab$^{-1}$, $C_{4b}^2$ can be probed at the per mille level.

The decay channel is nearly background-free at the LHeC after simple cuts.

Abstract

We study the exotic decay of the 125 GeV Higgs boson ($h$) into a pair of light spin-0 particles ($\phi$) which subsequently decays and results in a $4b$ final state. This decay mode is well motivated in the Next to Minimal Supersymmetric Standard Model (NMSSM) and extended Higgs sector models. Instead of searching at the Large Hadron Collider (LHC) and the High Luminosity Large Hadron Collider (HL-LHC) which are beset by large Standard Model (SM) backgrounds, we investigate this decay channel at the much cleaner Large Hadron Electron Collider (LHeC). With some simple selection cuts this channel becomes nearly free of background at this $ep$ machine, in stark contrast with the situation at the (HL-)LHC. With a parton level analysis we show that for the $\phi$ mass range $[20,60]GeV$, with $100\,fb^{-1}$ luminosity the LHeC is generally capable of constraining $C_{4b}^2\equiv\kappa_{V}^2\times\text{Br}(h\rightarrow\phi\phi)\times\text{Br}^2(\phi\rightarrow b\bar{b})$ ($\kappa_{V}$ denotes the $hVV(V=W,Z)$ coupling strength relative to the SM value) to a few percent level ($95\%$ CLs). With $1\,ab^{-1}$ luminosity $C_{4b}^2$ at a few per mille level can be probed. These sensitivities are much better than the HL-LHC performance and demonstrate the important role expected to be played by the LHeC in probing exotic Higgs decay processes, in addition to the already proposed invisible Higgs decay channel.