Top quark Kaluza - Klein mode mixing in the Randall - Sundrum bulk Standard Model and B → X

We study the top quark Kaluza-Klein (KK) mode mixing in the RandallSundrum (RS) scenario, where all the standard model (SM) fields except the Higgs field are in the bulk. To avoid the problems of FCNC, for all three generations the universal bulk fermion mass mψ are assumed. The degeneracy in the KK masses of quarks leads to the GIM cancellation KK-level by level. However, Yukawa mass terms for the top quark generate the mixing among its KK modes. The degeneracy in the KK masses of up-type quarks is broken and their contribution to FCNC is inevitable. The current measurements of Br(B → Xs + γ) with 99% CL strongly constrain the effective weak scale kEW : kEW > ∼ 2 TeV for mψ/k = −0.3 and kEW > ∼ 3 TeV for mψ/k = −0.4, where k is the AdS5 curvature. Moreover, high energy collider and rare B decays can play complementary roles to probe the effects of the RS-bulk SM: The mψ/k = −0.3 (mψ/k = −0.4) case generates larger (smaller) collider signatures but smaller (larger) b → sγ contribution.