The QCD Axion from Aligned Axions and Diphoton Excess

TL;DR

This paper proposes a model where multiple aligned axions with low decay constants can explain the QCD axion and potentially account for the 750 GeV diphoton excess, predicting new collider signatures and cosmological effects.

Contribution

It introduces a novel aligned axion framework with low decay constants that links QCD axion physics to collider phenomenology and cosmology.

Findings

Multiple axions can explain the diphoton excess at 750 GeV.

Predicted collider signatures include heavy axions and saxions at various energy scales.

The scenario naturally maintains high-quality Peccei-Quinn symmetry.

Abstract

We argue that the QCD axion can arise from many aligned axions with decay constants much smaller than the conventional axion window. If the typical decay constant is of {\cal O}{(100)} GeV to 1 TeV, one or more of the axions or saxions may account for the recently found diphoton excess at \sim 750 GeV. Our scenario predicts many axions and saxions coupled to gluons with decay constants of order the weak scale, and therefore many collider signatures by heavy axions and saxions will show up at different energy scales. In particular, if the inferred broad decay width is due to multiple axions or saxions, a non-trivial peak structure may become evident when more data is collected. We also discuss cosmological implications of the aligned QCD axion scenario. In the Appendix we give a possible UV completion and argue that the high quality of the Peccei-Quinn symmetry is naturally explained in our scenario.