LHC diphotons from electroweakly pair-produced composite pseudoscalars

Understand

Motivated by excess diphoton events reported by ATLAS and CMS, we show that composite pseudoscalars, bound states of heavy fermions under a new confining gauge theory, can be pair-produced by Drell-Yan production if the constituent particles are electrically charged.

• The decays of these pion-like bound states into two photons can explain the observed events near 750 GeV.
• The model predicts that there should be significant numbers of 4-photon events from decays of the pseudoscalar pairs, as well as same-sign dilepton pairs at a somewhat lower invariant mass, or multijet signals, coming from decays of charge-2 pseudoscalars.
• These states and their decays are necessary for avoiding stable charged baryon-like relics in the new confining sector.