Dynamical electroweak symmetry breaking from deformed AdS space: Vector mesons and effective couplings

We study a modification of the five-dimensional description of dynamical electroweak 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 cutoff. This study shows that observables, such as the precision parameter Ŝ, 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 electroweak 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 Large Hadron Collider 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 cutoff in the IR.