Diphotons from Diaxions

TL;DR

This paper explores a model where a 750 GeV scalar decays into pseudo-Nambu-Goldstone bosons, which then decay into highly boosted photon pairs that mimic single photons, explaining the diphoton excess.

Contribution

It provides a model-independent analysis showing how axion-like particles can explain the diphoton excess with large width and prompt decay constraints.

Findings

Can explain the observed signal with a 200 MeV axion mass.

Requires large axion-photon coupling and new charged particles at TeV scale.

Reduces the multiplicity of new fields compared to direct diphoton models.

Abstract

We study models in which the 750 GeV diphoton excess is due to a scalar decaying to two pseudo-Nambu-Goldstone bosons that subsequently decay into two pairs of highly boosted photons, misidentified as individual photons. Performing a model independent analysis we find that, with axion mass around $200$ MeV, this class of theories can naturally explain the observed signal with a large width, without violating monojet constraints. At the same time the requirement of a prompt axion decay can be satisfied only with a relatively large axion-photon coupling, leading to many new charged particles at the TeV scale. However, the required multiplicities of such fields is still moderately reduced relative to models with direct diphoton production.