On the maximal diphoton width

TL;DR

This paper investigates the maximum possible diphoton decay width of a neutral scalar at 750 GeV, considering loop contributions, stability bounds, and the effects of additional gauge symmetries, with implications for collider searches and Dark Matter.

Contribution

It provides a detailed calculation of the maximal diphoton width constrained by stability bounds and explores how extra gauge symmetries can relax these limits.

Findings

Maximal diphoton width depends on the theory's cutoff scale.

Extra gauge symmetry can weaken stability bounds.

Connections with Dark Matter and collider probes are discussed.

Abstract

Motivated by the 750 GeV diphoton excess found at LHC, we compute the maximal width into $\gamma\gamma$ that a neutral scalar can acquire through a loop of charged fermions or scalars as function of the maximal scale at which the theory holds, taking into account vacuum (meta)stability bounds. We show how an extra gauge symmetry can qualitatively weaken such bounds, and explore collider probes and connections with Dark Matter.