# Dark and Bright Signatures of Di-Higgs Production

## TL;DR

This paper explores the detection of di-Higgs production involving invisible decays at the LHC, proposing a multichannel approach that enhances sensitivity to dark matter signatures and constrains the Higgs self-coupling.

## Contribution

It introduces a combined analysis of gamma-gamma and b-bbar channels with missing energy, demonstrating improved bounds on Higgs properties and dark matter detection prospects.

## Key findings

- The gamma-gamma + missing energy channel is competitive with b-bbar + missing energy after optimized cuts.
- Multivariate analysis yields stronger bounds on Higgs trilinear coupling for low invisible branching fractions.
- Combining three channels enhances the search sensitivity for non-standard Higgs self-couplings with invisible decays.

## Abstract

If the Higgs boson decays to a pair of invisible particles, the number of di-Higgs events, where each Higgs decay into Standard Model (SM) particles, are reduced by a factor of two-third taking into account the current LHC bound on invisible decay width of the Higgs boson. We investigate the sensitivity of the upcoming high luminosity run of the LHC to di-Higgs production and subsequent decay to dark matter in the context of the singlet scalar extension of the SM augmented by a fermionic dark matter in the dark and bright channel $\gamma\gamma+\not\!\! E_T$. Once systematic uncertainties on background yields are considered, this dark and bright channel presents competitive limits than $b\bar{b}+\not\!\! E_T$ after a careful tuning of the kinematical cuts that raise the signal over background ratio. We further show that in a multivariate analysis, for an invisible branching fraction as low as $\sim 10$%, we obtain stronger bounds for the Higgs trilinear coupling from the $\gamma\gamma+\not\!\! E_T$ channel compared to the $b\bar{b}\gamma\gamma$ final state. Finally, we demonstrate that the three channels $\gamma\gamma+\not\!\! E_T$, $b\bar{b}+\not\!\! E_T$ and $b\bar{b}\gamma\gamma$, complement each other in the search for di-Higgs production with non-SM trilinear couplings when an invisible decay mode is present.