Diphoton signals from colorless hidden quarkonia

Abstract

We show that quarkonialike states of a hidden $\mathrm{SU}(N)$ gauge group can account for the 750 GeV diphoton excess observed by ATLAS and CMS, even with constituents carrying standard model hypercharge only. The required hypercharge is modest, varying between about 1.3--1.6 for strong $\mathrm{SU}(N)$ coupling to 2--3 for weak $\mathrm{SU}(N)$ coupling, for $N=3$, 4. This scenario predicts a variety of diphoton and multiphoton resonances, as well as photons from continuum pair production, and possibly exotic decays into standard model fermions, with no significant multijet resonances.