Running after Diphoton

Understand

A very plausible explanation for the recently observed diphoton excess at the 13 TeV LHC is a (pseudo)scalar with mass around 750 GeV, which couples to a gluon pair and to a photon pair through loops involving vector-like quarks (VLQs).

• To accommodate the observed rate, the required Yukawa couplings tend to be large.
• A large Yukawa coupling would rapidly run up with the scale and quickly reach the perturbativity bound, indicating that new physics, possibly with a strong dynamics origin, is near by.
• The case becomes stronger especially if the ATLAS observation of a large width persists.