Radion Phenomenology in Realistic Warped Space Models

TL;DR

This paper explores the properties and detection prospects of the radion in realistic warped space models, focusing on its couplings, decay channels, and signals at the LHC, with implications for electroweak symmetry breaking.

Contribution

It provides a detailed calculation of radion couplings to bulk fields, including loop effects, and analyzes the LHC discovery potential considering brane-localized kinetic terms.

Findings

Gamma-gamma signal can be enhanced over SM Higgs for low RS scale.

Signal significance varies with brane-localized kinetic terms.

4 lepton channel useful for larger radion masses.

Abstract

We investigate the phenomenology of the Randall-Sundrum radion in realistic models of electroweak symmetry breaking with bulk gauge and fermion fields, since the radion may turn out to be the lightest particle in such models. We calculate the coupling of the radion in such scenarios to bulk fermion and gauge modes. Special attention needs to be devoted to the coupling to massless gauge fields (photon, gluon), since it is well known that loop effects may be important for these fields. We also present a detailed explanation of these couplings from the CFT interpretation. We then use these couplings to determine the radion branching fractions and discuss some of the discovery potential of the LHC for the radion. We find that the gamma-gamma signal is enhanced over most of the range of the radion mass over the gamma-gamma signal of a SM Higgs, as long as the RS scale is sufficiently low. However, the signal significance depends strongly on free parameters that characterize the magnitude of bare brane-localized kinetic terms for the massless gauge fields. In the absence of such terms, the signal can be be enhanced over the traditional RS1 models (where all standard model fields are localized on the IR brane), but the signal can also be reduced compared to RS1 if the brane localized terms are sizeable. We also show that for larger radion masses, where the gamma-gamma signal is no longer significant, one can use the usual 4 lepton signal to discover the radion.