Symmetries Behind the 750 GeV Diphoton Excess

TL;DR

This paper proposes a model where a 750 GeV scalar resonance explains the diphoton excess at the LHC, linking it to spontaneous symmetry breaking, anomaly cancellation, and dark matter, fitting experimental data.

Contribution

It introduces a new gauge symmetry-based model with a scalar dark matter candidate that accounts for the diphoton excess and its decay width at the LHC.

Findings

The model explains the observed cross section and decay width of the resonance.

The scalar S has negligible mixing with the Higgs but strong coupling to dark matter.

The model is consistent with current experimental constraints.

Abstract

A 750 GeV resonance has been observed at the Run 2 LHC in the diphoton channel. In this paper, we explain this resonance as a CP-even scalar, S, that triggers the spontaneous breaking of local $U(1)_B$ or $U(1)_{B+L}$ gauge symmetries. S couples to gluon and photon pairs at the one-loop level, where particles running in the loop are originally introduced to cancel anomalies. The gluon fusion is the dominate production channel of S at the LHC. The model automatically contains a scalar dark matter candidate, stabilized by the new gauge symmetry. Our study shows that both the observed production cross section at the LHC and the best fit decay width of S can be explained in this concrete model, without conflicting with any experimental data. Constraints on couplings of S are studied, which shows a negligible mixing with the standard model Higgs boson but sizable coupling with the dark matter.