A NATURAL EXTENSION OF STANDARD WARPED HIGHER-DIMENSIONAL COMPACTIFICATIONS: THEORY AND PHENOMENOLOGY

Abstract

Warped higher-dimensional compactifications with ``bulk'' standard model, or their AdS/CFT dual as the purely 4D scenario of Higgs compositeness and partial compositeness, offer an elegant approach to resolving the electroweak hierarchy problem as well as the origins of flavor structure. However, low-energy electroweak/flavor/CP constraints and the absence of non-standard physics at LHC Run 1 suggest that a ``little hierarchy problem'' remains, and that the new physics underlying naturalness may lie out of LHC reach. Assuming this to be the case, we show that there is a simple and natural extension of the minimal warped model in the Randall-Sundrum framework, in which matter, gauge and gravitational fields propagate modestly different degrees into the IR of the warped dimension, resulting in rich and striking consequences for the LHC (and beyond).

The LHC-accessible part of the new physics is AdS/CFT dual to the mechanism of ``vectorlike confinement'', with TeV-scale Kaluza-Klein excitations of the gauge and gravitational fields dual to spin-0,1,2 composites. Unlike the minimal warped model, these low-lying excitations have predominantly flavor-blind and flavor/CP-safe interactions with the standard model. In addition, the usual leading decay modes of the lightest KK gauge bosons into top and Higgs bosons are suppressed. This effect permits erstwhile subdominant channels to become significant. These include flavor-universal decays to all pairs of SM fermions, and a novel channel — decay to a radion and a SM gauge boson, followed by radion decay to a pair of SM gauge bosons. We present a detailed phenomenological study of the latter cascade decay processes.

Remarkably, this scenario also predicts small deviations from flavor-blindness originating from virtual effects of Higgs/top compositeness at ∼ O(10) TeV, with subdominant resonance decays into a pair of Higgs/top-rich final states, giving the LHC an early ``preview'' of the nature of the resolution of the hierarchy problem. Discoveries of this type at LHC Run 2 would thereby anticipate (and set a target for) even more explicit explorations of Higgs compositeness at a 100 TeV collider, or for next-generation flavor tests.