750 GeV diphoton resonance in a visible heavy QCD axion model

Understand

In this paper, we revisit a visible heavy QCD axion model in light of the recent reports on the $750$ GeV diphoton resonance by the ATLAS and CMS experiments.

• In this model, the axion is made heavy with the help of the mirror copied sector of the Standard Model while the successful Peccei-Quinn mechanism is kept intact.
• We identify the $750$ GeV resonance as the scalar boson associated with spontaneous breaking of the Peccei-Quinn symmetry which mainly decays into a pair of the axions.
• We find that the mixings between the axion and $\eta$ and $\eta'$ play important roles in its decays and the resultant branching ratio into two photons.