Precision measurements and fermion geography in the Randall-Sundrum model revisited

Abstract

We re-examine the implications of allowing fermion fields to propagate in the five-dimensional bulk of the Randall-Sundrum (RS) localized gravity model. We find that mixing between the Standard Model top quark and its Kaluza Klein excitations generates large contributions to the ρ parameter and consequently restricts the fundamental RS scale to lie above 100 TeV. To circumvent this bound we propose a 'mixed' scenario which localizes the third generation fermions on the TeV brane and allows the lighter generations to propagate in the full five-dimensional bulk. We show that this construction naturally reproduces the observed mc/mt and m s/mb hierarchies. We explore the signatures of this scenario in precision measurements and future high energy collider experiments. We find that the region of parameter space that addresses the hierarchies of fermion Yukawa couplings permits a Higgs boson with a mass of 500 GeV and remains otherwise invisible at the LHC. However, the entire parameter region consistent with electroweak precision data is testable at future linear colliders. We briefly discuss possible constraints on this scenario arising from flavor changing neutral currents. © SISSA/ISAS 2002.