Multi-Gauge-Boson Vertices and Chiral Lagrangian Parameters in Higgsless Models with Ideal Fermion Delocalization

Abstract

Higgsless models with fermions whose SU(2) properties are "ideally delocalized," such that the fermion's probability distribution is appropriately related to the W boson wavefunction, have been shown to minimize deviations in precision electroweak parameters. As contributions to the S parameter vanish to leading order, current constraints on these models arise from limits on deviations in multi-gauge-boson vertices. We compute the form of the triple and quartic gauge boson vertices in these models and show that these constraints provide lower bounds only of order a few hundred GeV on the masses of the lightest KK resonances. Higgsless models with ideal fermion delocalization provide an example of extended electroweak gauge interactions with suppressed couplings of fermions to extra gauge-bosons, and these are the only models for which triple-gauge-vertex measurements provide meaningful constraints. We relate the multi-gauge couplings to parameters of the electroweak chiral Lagrangian, and the parameters obtained in these SU(2) x SU(2) models apply equally to the corresponding five dimensional gauge theory models of QCD. We also discuss the collider phenomenology of the KK resonances in models with ideal delocalization. These resonances are found to be fermiophobic, therefore traditional direct collider searches are not sensitive to them and measurements of gauge-boson scattering will be needed to find them.