Broad Diphotons from Narrow States

Understand

ATLAS and CMS have each reported a modest diphoton excess consistent with the decay of a broad resonance at ~ 750 GeV.

• We show how this signal can arise in a weakly coupled theory comprised solely of narrow width particles.
• In particular, if the decaying particle is produced off-shell, then the associated diphoton resonance will have a broad, adjustable width.
• We present simplified models which explain the diphoton excess through the three-body decay of a scalar or fermion.