The Diphoton Excess, Low Energy Theorem and the 331 Model

TL;DR

This paper interprets the 750 GeV diphoton excess as a heavy scalar in the 331 model, analyzing its couplings and contributions from heavy particles, and suggests charged scalars are essential for explaining the excess.

Contribution

It applies the low energy theorem to calculate effective couplings of the scalar to gauge bosons within the 331 model, highlighting the importance of charged scalars for the diphoton excess.

Findings

Heavy quark and lepton loops alone cannot account for the diphoton excess.

Charged scalars play a crucial role in explaining the observed diphoton signal.

The model also offers an explanation for the 2 TeV diboson excess via the $Z'$ boson.

Abstract

We interpret the diphoton anomaly as a heavy scalar $H_3$ in the so-called 331 model. The scalar is responsible for breaking the $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$ gauge symmetry down to the standard model electroweak gauge group. It mainly couples to the standard model gluons and photons through quantum loops involving heavy quarks and leptons. Those quarks and leptons, in together with the SM quarks and leptons, form the fundamental representation of the 331 model. We use low energy theorem to calculate effective coupling of $H_3gg$, $H_3\gamma\gamma$, $H_3ZZ$, $H_3WW$ and $H_3Z\gamma$. The analytical results can be applied to new physics models satisfying the low energy theorem. We show that the heavy quark and lepton contribution cannot produce enough diphoton pairs. It is crucial to include the contribution of charged scalars to explain the diphoton excess. The extra neutral $Z^\prime$ boson could also explain the 2 TeV diboson excess observed at the LHC Run-I.