The 750 GeV Diphoton Excess May Not Imply a 750 GeV Resonance

TL;DR

This paper explores alternative explanations for the 750 GeV diphoton excess, proposing cascade decay models involving heavier resonances and invisible particles that can mimic the observed signal without a new broad resonance.

Contribution

It introduces three specific cascade decay topologies as non-standard interpretations of the diphoton excess, fitting the data without requiring a broad resonance.

Findings

Cascade decay models can fit the observed data well.

Moderate missing transverse energy can result from these models.

Preferred mass parameters are identified for each topology.

Abstract

We discuss non-standard interpretations of the 750 GeV diphoton excess recently reported by the ATLAS and CMS Collaborations which do not involve a new, relatively broad, resonance with a mass near 750 GeV. Instead, we consider the sequential cascade decay of a much heavier, possibly quite narrow, resonance into two photons along with one or more invisible particles. The resulting diphoton invariant mass signal is generically rather broad, as suggested by the data. We examine three specific event topologies - the antler, the sandwich, and the 2-step cascade decay, and show that they all can provide a good fit to the observed published data. In each case, we delineate the preferred mass parameter space selected by the best fit. In spite of the presence of invisible particles in the final state, the measured missing transverse energy is moderate, due to its anti- correlation with the diphoton invariant mass. We comment on the future prospects of discriminating with higher statistics between our scenarios, as well as from more conventional interpretations.