Effective fermion couplings in warped 5D Higgsless theories

Abstract

We consider a five dimensional SU(2) gauge theory with fermions in the bulk and with additional SU(2) and U(1) kinetic terms on the branes. The electroweak breaking is obtained by boundary conditions. After deconstruction, fermions in the bulk are eliminated by using their equations of motion. In this way Standard Model fermion mass terms and direct couplings to the internal gauge bosons of the moose are generated. The presence of these new couplings gives a new contribution to the epsilon_3 parameter in addition to the gauge boson term. This allows the possibility of a cancellation between the two contributions, which can be local (site by site) or global. Going back to the continuum, we show that the implementation of local cancellation in any generic warped metric leaves massless fermions. This is due to the presence of one horizon on the infrared brane. However we can require a global cancellation of the new physics contributions to the epsilon_3 parameter. This fixes relations among the warp factor and the parameters of the fermion and gauge sectors.