Comments on the diphoton excess: critical reappraisal of effective field theory interpretations

TL;DR

This paper critically reexamines the diphoton excess using effective field theory, highlighting correlations among decay channels and proposing methods to distinguish between different models and hidden decays.

Contribution

It provides a detailed analysis of EFT interpretations of the diphoton excess, emphasizing correlated decay channels and experimental strategies to constrain new physics.

Findings

Two of three decay modes must occur with non-zero rates in EFT.

Branching ratios are highly correlated within EFT.

VBF measurements can help identify hidden decays.

Abstract

We consider the diphoton excess observed by ATLAS and CMS using the most up-to-date data and estimate the preferred enhancement in the production rate between 8 TeV and 13 TeV. Within the framework of effective field theory (EFT), we then show that for both spin-0 and spin-2 Standard Model (SM) gauge-singlet resonances, two of the three processes S to ZZ, S to Z gamma, and S to WW must occur with a non-zero rate. Moreover, we demonstrate that these branching ratios are highly correlated in the EFT. Couplings of S to additional SM states may be constrained and differentiated by comparing the S production rates with and without the vector-boson fusion (VBF) cuts. We find that for a given VBF to inclusive production ratio there is maximum rate of S to gauge bosons, b b-bar, and lighter quark anti-quark pairs. Simultaneous measurements of the width and the VBF ratio may be able to point towards the existence of hidden decays.