Invisible Higgs Decay at the LHeC

TL;DR

This paper assesses the Large Hadron Electron Collider's ability to detect invisible Higgs decays, highlighting its potential to probe non-standard decay modes with high sensitivity in a specific production channel.

Contribution

It provides the first detailed sensitivity estimate for invisible Higgs decays at the LHeC using a cut-based analysis in the neutral current channel.

Findings

LHeC can probe Br(h→invisible) down to 6% at 2σ with 1 ab^{-1} luminosity.

Good lepton veto, especially for hadronic τ, is crucial for background suppression.

The study emphasizes the role of lepton-hadron colliders in precision Higgs and new resonance studies.

Abstract

The possibility that the 125 GeV Higgs boson may decay into invisible non-standard-model (non-SM) particles is theoretically and phenomenologically intriguing. In this letter we investigate the sensitivity of the Large Hadron Electron Collider (LHeC) to an invisibly decaying Higgs, in its proposed high luminosity running mode. We focus on the neutral current Higgs production channel which offers more kinematical handles than its charged current counterpart. The signal contains one electron, one jet and large missing energy. With a cut-based parton level analysis, we estimate that if the $hZZ$ coupling is at its standard model (SM) value, then assuming an integrated luminosity of $1\,\mbox{ab}^{-1}$ the LHeC with the proposed 60 GeV electron beam (with $-0.9$ polarization) and 7 TeV proton beam is capable of probing $\mathrm{Br}(h\rightarrow E\!\!\!\!/_T)=6\%$ at $2\sigma$ level. Good lepton veto performance (especially hadronic $\tau$ veto) in the forward region is crucial to the suppression of the dominant $Wje$ background. We also explicitly point out the important role that may be played by the LHeC in probing a wide class of exotic Higgs decay processes and emphasize the general function of lepton-hadron colliders in precision study of new resonances after their discovery in hadron-hadron collisions.