Confronting dark matter with the diphoton excess from a parent resonance decay

TL;DR

This paper proposes a hierarchical model with a parent resonance decaying into two 750 GeV particles, incorporating a dark matter candidate, to better explain the diphoton excess observed at the LHC while remaining consistent with other experimental constraints.

Contribution

It introduces a novel hierarchical framework with a parent resonance and dark matter candidate, improving the fit to LHC data and addressing dark matter phenomenology.

Findings

The model fits the diphoton excess data more effectively than simpler interpretations.

Inclusion of dark matter candidate aligns with relic density and indirect detection constraints.

The framework remains consistent with existing LHC search results.

Abstract

A diphoton excess with an invariant mass of about 750 GeV has been recently reported by both ATLAS and CMS experiments at LHC. While the simplest interpretation requires the resonant production of a 750 GeV (pseudo)scalar, here we consider an alternative setup, with an additional heavy parent particle which decays into a pair of 750 GeV resonances. This configuration improves the agreement between the 8 TeV and 13 TeV data. Moreover, we include a dark matter candidate in the form of a Majorana fermion which interacts through the 750 GeV portal. The invisible decays of the light resonance help to suppress additional decay channels into Standard Model particles in association with the diphoton signal. We realise our hierarchical framework in the context of an effective theory, and we analyse the diphoton signal as well as the consistency with other LHC searches. We finally address the interplay of the LHC results with the dark matter phenomenology, namely the compatibility with the relic density abundance and the indirect detection bounds.