Dynamical electro-weak symmetry breaking from deformed AdS: vector mesons and effective couplings

TL;DR

This paper explores how modifications to the five-dimensional AdS model influence electroweak symmetry breaking, affecting composite state couplings and phenomenological bounds relevant for LHC physics.

Contribution

It introduces a power-law deformation of the AdS background that impacts composite state couplings and electroweak symmetry breaking scales.

Findings

Couplings of lightest composite states are highly sensitive to IR region dynamics.

Deformation allows chiral symmetry breaking at higher scales.

Bounds on heavy resonance masses at LHC are generally lower than in pure AdS models.

Abstract

We study a modification of the five-dimensional description of dynamical electro-weak symmetry breaking inspired by the AdS/CFT correspondence. Conformal symmetry is broken in the low-energy region near the IR brane by a power-law departure from the pure AdS background. Such a modification--while not spoiling the identification of the IR brane with the scale of confinement-- has a dramatic effect on both the coupling of the first composite states to the standard model currents and their self-couplings. Chiral symmetry breaking can take place at a scale larger than the IR cut-off. This study shows that observables, such as the precision parameter $\hat{S}$, which depend on the couplings of the lightest composite states to the currents are very sensitive to the details of the dynamics in the low energy region where conformal symmetry is lost and electro-weak symmetry is broken just above the scale of confinement. Therefore results of calculations of these observables in AdS/CFT inspired scenarios should be interpreted conservatively. The most important phenomenological consequence for physics at the LHC is that the bound on the mass scale of the heavy excitations (technirho mesons) in a realistic model is in general lower than in the pure AdS background with a simple hard-wall cut off in the IR.