A pseudoscalar decaying to photon pairs in the early LHC Run 2 data

Understand

In this paper we explore the possibility of a pseudoscalar resonance to account for the 750 GeV diphoton excess observed both at ATLAS and at CMS.

• We analyze the ingredients needed from the low energy perspective to obtain a sufficiently large diphoton rate to explain the signal while avoiding constraints from other channels.
• Additionally, we point out composite Higgs models in which one can naturally obtain a pseudoscalar at the 750 GeV mass scale and we estimate the pseudoscalar couplings to standard model particles that one would have in such models.
• A generic feature of models that can explain the excess is the presence of new particles in addition to the 750 GeV state.