Phenomenology of Infrared Smooth Warped Extra Dimensions

TL;DR

This paper investigates how IR geometry variations in warped extra dimensions influence the mass spectrum and couplings of KK modes, showing significant shifts but maintaining key experimental constraints.

Contribution

It introduces a mass gap metric model that interpolates between AdS and flat space, analyzing its impact on KK phenomenology and experimental bounds.

Findings

Mass spectrum shifts up to a factor of 2

Coupling increases up to a factor of 10

Constraints like m_KK > 3 TeV remain robust

Abstract

We study the effect of the infrared (IR) geometry on the phenomenology of warped extra dimensions with gauge and fermion fields in the bulk. We focus in particular on a "mass gap" metric which is AdS in the ultraviolet, but asymptotes to flat space in the IR, breaking conformal symmetry. These metrics can be dialed to approximate well the geometries arising in certain classes of warped string compactifications. We find, similar to our earlier results on the Kaluza-Klein (KK) graviton, that these metrics give rise to phenomenologically significant shifts in the separation of KK gauge modes in the mass spectrum (up to factors of ~2) and their couplings to IR localized fields (up to factors of ~5-10 increase). We find that, despite shifts in the spectra, the constraint m_KK > 3 TeV from S remains robust in the class of 5-d mass gap metrics, and that the change to T is not significant enough to remove the need for custodial symmetry.