Radion-Higgs mixing effects on bounds from LHC Higgs Searches

TL;DR

This paper investigates how radion-Higgs mixing affects LHC Higgs search bounds, analyzing current data to constrain radion parameters and exploring scenarios where the Higgs could be hidden due to suppressed couplings.

Contribution

It provides the first comprehensive analysis of radion-Higgs mixing effects on LHC Higgs search constraints and identifies parameter regions where the radion can evade detection.

Findings

Radion can have a mass similar to the Higgs and still evade current bounds.

Mixing parameter $\xi$ significantly influences radion phenomenology.

Current LHC data can exclude certain radion parameter regions.

Abstract

The radion, a scalar particle associated with the radius of a compact warped extra dimension, may be the lightest new particle in this class of models. Its couplings to SM particles are proportional to the their masses, similar to the usual Higgs boson, but suppressed by a scale $\Lambda_r$, the radion vacuum expectation value. The main differences are the coupling to massless gauge bosons that receives contribution from the trace anomaly of the energy-momentum tensor due to the the nonvanishing $\beta$ functions and the mixing with the Higgs boson arising from a nonminimal coupling to gravity parametrized by a dimensionless coefficient $\xi$. In particular, these differences can result in significant modifications of the radion phenomenology.We use current LHC data on Higgs searches to find exclusion regions on the parameters of a radion model, $\Lambda_r$, $\xi$ and the radion mass $m_r$. We find that, even for low values of $\Lambda_r$, the radion can still have a mass in the region where the Standard Model Higgs has been excluded, for a narrow range of values for the mixing parameter. Some signals at the LHC for this scenario are discussed.We also find that it is possible to hide the Higgs boson in the current searches in this model, due to a suppression of its couplings.