Re-opening dark matter windows compatible with a diphoton excess

TL;DR

This paper proposes a model where a scalar decays into pseudo-Goldstone bosons, which then produce collimated photons that mimic a diphoton excess, compatible with dark matter constraints and relic density.

Contribution

It introduces a minimal spontaneous symmetry breaking model linking a scalar, pseudo-Goldstone bosons, and dark matter to explain the 750 GeV diphoton excess.

Findings

Model explains the 750 GeV diphoton excess with collimated photon pairs.

Compatible with observed dark matter relic density.

Not excluded by current detection experiments.

Abstract

We investigate a simple setup in which an excess in the di-photon invariant mass distribution around $750$ GeV, as seen by the ATLAS and CMS collaborations, is originated through a pair of collimated photon pairs. In this framework a scalar state $s$ decays into two light pseudo-Goldstone bosons $a$, each of which subsequently decays into a pair of collimated photons which are misidentified as a single photon. In a minimal context of spontaneous symmetry breaking, we show that coupling a complex scalar field $\Phi=(s+ia)/\sqrt{2}$ to a fermionic dark matter candidate $\chi$, also responsible for generating its mass, allows for the correct relic density in a large region of the parameter space, while not being excluded by the direct or indirect detection experiments. Moreover, the correct relic abundance can naturally co-exist with a relatively large width for the resonant field $s$.