On dilatons and the LHC diphoton excess

TL;DR

This paper explores soft wall models with a light dilaton, analyzing their compatibility with electroweak tests and potential explanations for the LHC diphoton excess, including a 750 GeV dilaton candidate.

Contribution

It demonstrates how soft wall models can embed a light dilaton compatible with experimental constraints and proposes a 750 GeV dilaton as a possible explanation for the LHC diphoton excess.

Findings

Models with a light dilaton can pass electroweak precision tests at ~2 TeV scale.

A 125 GeV dilaton as a Higgs impostor is disfavored.

A 750 GeV dilaton can potentially explain the LHC diphoton excess.

Abstract

We study soft wall models that can embed the Standard Model and a naturally light dilaton. Exploiting the full capabilities of these models we identify the parameter space that allows to pass Electroweak Precision Tests with a moderate Kaluza-Klein scale, around $2$ TeV. We analyze the coupling of the dilaton with Standard Model (SM) fields in the bulk, and discuss two applications: i) Models with a light dilaton as the first particle beyond the SM pass quite easily all observational tests even with a dilaton lighter than the Higgs. However the possibility of a 125 GeV dilaton as a Higgs impostor is essentially disfavored; ii) We show how to extend the soft wall models to realize a 750 GeV dilaton that could explain the recently reported diphoton excess at the LHC.