Electroweak and Flavour Structure of a Warped Extra Dimension with Custodial Protection

TL;DR

This paper analyzes a warped extra dimension model with a specific gauge group, highlighting its custodial symmetry features that protect against large electroweak corrections and detailing the mass matrices and interactions of gauge and fermion KK modes.

Contribution

It provides an analytical diagonalization of gauge and fermion mass matrices and derives Feynman rules for a warped extra dimension model with custodial symmetry.

Findings

Custodial symmetry suppresses large T parameter contributions.

Explicit mass matrices for gauge and fermion KK modes are derived.

Complete Feynman rules for interactions are provided.

Abstract

We present the electroweak and flavour structure of a model with a warped extra dimension and the bulk gauge group SU(3) x SU(2)_L x SU(2)_R x P_LR x U(1)_X. The presence of SU(2)_R implies an unbroken custodial symmetry in the Higgs system allowing to eliminate large contributions to the T parameter, whereas the P_LR symmetry and the enlarged fermion representations provide a custodial symmetry for flavour diagonal and flavour changing couplings of the SM Z boson to left-handed down-type quarks. We diagonalise analytically the mass matrices of charged and neutral gauge bosons including the first KK modes. We present the mass matrices for quarks including heavy KK modes and discuss the neutral and charged currents involving light and heavy fields. We give the corresponding complete set of Feynman rules in the unitary gauge.