Bulk fermions in warped models with a soft wall

Abstract

We study bulk fermions in models with warped extra dimensions in the presence of a soft wall. Fermions can acquire a position dependent bulk Dirac mass that shields them from the deep infrared, allowing for a systematic expansion in which electroweak symmetry breaking effects are treated perturbatively. Using this expansion, we analyze properties of bulk fermions in the soft-wall background. These properties include the realization of nontrivial boundary conditions that simulate the ones commonly used in hard-wall models, the analysis of the flavor structure of the model and the implications of a heavy top. We implement a soft-wall model of electroweak symmetry breaking with custodial symmetry and fermions propagating in the bulk. We find a lower bound on the masses of the first bosonic resonances, after including the effects of the top sector on electroweak precision observables for the first time, of ${m}_{KK}\ensuremath{\gtrsim}1--3\text{ }\text{ }\mathrm{TeV}$ at the 95% C.L., depending on the details of the Higgs, and discuss the implications of our results for LHC phenomenology.