A 750 GeV Portal: LHC Phenomenology and Dark Matter Candidates

TL;DR

This paper explores a theoretical extension of the Standard Model with new scalar and fermion particles to explain the 750 GeV diphoton excess and dark matter properties, analyzing collider and astrophysical constraints.

Contribution

It introduces an effective field theory with a 750 GeV scalar and a stable fermion, examining collider signals and dark matter phenomenology in this framework.

Findings

Scalar portal models are near direct detection limits if gluon fusion dominates.

Pseudo-scalar models face constraints from photon line limits and mono-jet searches.

The theory can explain the diphoton excess while remaining consistent with existing bounds.

Abstract

We study the effective field theory obtained by extending the Standard Model field content with two singlets: a 750 GeV (pseudo-)scalar and a stable fermion. Accounting for collider productions initiated by both gluon and photon fusion, we investigate where the theory is consistent with both the LHC diphoton excess and bounds from Run 1. We analyze dark matter phenomenology in such regions, including relic density constraints as well as collider, direct, and indirect bounds. Scalar portal dark matter models are very close to limits from direct detection and mono-jet searches if gluon fusion dominates, and not constrained at all otherwise. Pseudo-scalar models are challenged by photon line limits and mono-jet searches in most of the parameter space.