Top quark Kaluza-Klein mode mixing in the Randall-Sundrum bulk Standard Model and Constraint from ∆ρ

The Randall-Sundrum (RS) scenario with all the standard model (SM) fermions and gauge bosons in the bulk is phenomenologically studied. Even though the simple assumption of universal bulk fermion mass mψ leads to the same Kaluza-Klein (KK) mass spectrum for all the SM fermions and thus suppresses new contributions to Flavor-Changing-Neutral-Current (FCNC) and the ρ parameter, large Yukawa coupling of the top quark generates its KK mode mixing and breaks the degeneracy: unacceptably large contribution to ∆ρ occurs. With a different bulk fermion mass to SU(2) singlet bottom quark, we demonstrate that there exists some parameter space to satisfy the ∆ρ constraint.