Bulk Fermions in Warped Models with a Soft Wall

TL;DR

This paper investigates bulk fermions in warped extra-dimensional models with a soft wall, developing a perturbative approach to analyze their properties, flavor structure, and electroweak symmetry breaking effects, with implications for collider phenomenology.

Contribution

It introduces a systematic expansion method for bulk fermions in soft wall models, including a detailed analysis of boundary conditions, flavor structure, and electroweak symmetry breaking effects.

Findings

Lower bound on first bosonic resonance masses: 1-3 TeV.

Electroweak precision constraints depend on Higgs details.

Implications for LHC searches for new resonances.

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 non-trivial 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} \gtrsim 1-3 TeV at the 95% C.L., depending on the details of the Higgs, and discuss the implications of our results for LHC phenomenology.