Asymmetric Dark Matter Bound State

TL;DR

This paper introduces a novel collider signature for asymmetric scalar dark matter involving an unstable bound state (ADMonium) that can be produced via Higgs portals and decay into electron pairs, offering a new way to search for dark matter at the LHC.

Contribution

It proposes a new collider phenomenology involving ADMonium formation and decay, connecting dark matter self-interactions with Higgs portal physics and LHC signatures.

Findings

ADMonium can be produced with sizable cross section at the LHC.

The decay of ADMonium into electron pairs can mimic di-photon signals.

The framework provides a potential explanation for heavy di-photon resonance searches.

Abstract

We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local $U(1)_d$ symmetry which is broken at a low scale and provides a light gauge boson $X$. The dark gauge coupling is strong and then ADM can annihilate away into $X$-pair effectively. Therefore, the ADM can form bound state due to its large self-interaction via $X$ mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with $b\bar b$. The resulting signature at the LHC depends on the decays of $X$. In this paper we consider a case of particular interest: $pp\ra b\bar b+ {\rm ADMonium}$ followed by ${\rm ADMonium}\ra 2X\ra 2e^+e^-$ where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC.