Flavor structure of warped extra dimension models

Abstract

We recently showed, in hep-ph/0406101, that warped extra dimensional models with bulk custodial symmetry and few TeV KK masses lead to striking signals at B-factories. In this paper, using a spurion analysis, we systematically study the flavor structure of models that belong to the above class. In particular we find that the profiles of the zero modes, which are similar in all these models, essentially control the underlying flavor structure. This implies that our results are robust and model independent in this class of models. We discuss in detail the origin of the signals in B-physics. We also briefly study other NP signatures that arise in rare K decays (K → πνν), in rare top decays [t → cγ(Z, gluon)] and the possibilty of CP asymmetries in D 0 decays to CP eigenstates such as KSπ 0 and others. Finally we demonstrate that with light KK masses, ∼ 3 TeV, the above class of models with anarchic 5D Yukawas has a "CP problem" since contributions to the neutron electric dipole moment are roughly 20 times larger than the current experimental bound. Using AdS/CFT correspondence, these extra-dimensional models are dual to a purely 4D strongly coupled conformal Higgs sector thus enhancing their appeal. 1

Model-independent constraints on ΔF= 2 operators and the scale of new physics

“…In particular, we find that the scale of heavy particles mediating tree-level FCNC in models of NMFV must lie above ∼ 60 TeV, making them undetectable at the LHC. This bound applies for instance to the Kaluza-Klein excitations of gauge bosons in a large class of models with (warped) extra dimensions [21]. Flavour physics remains the main avenue to probe such extensions of the SM.…”

“…This condition is realized in models in which right-handed currents also contribute to FCNC processes, but with the same hierarchical structure in the mixing angles as in the SM left-handed currents. Given the order-of-magnitude equalities m d /m b ∼ |V td |, m s /m b ∼ |V ts |, bounds obtained in this scenario are also of interest for extra-dimensional models with FCNC couplings suppressed linearly with quark masses [21]. Clearly, given the QCD and, for K 0 −K 0 mixing, chiral enhancement of NP operators, the constraints on the NP scale are much stronger for NMFV than for MFV, as shown explicitly in the next section.…”

Combining direct & indirect kaon CP violation to constrain the warped KK scale

“…Within the RS, this yields extra protection against excess of flavour changing neutral current (FCNC) processes in the form of RS-GIM [3]. A residual little CP problem is, however, still found in the form of too large contributions to the neutron electric dipole moment [3] and sizable contributions to K [4,5,6,7] (see also [8] for some related recent RS flavour studies). Given an IR-localized Higgs field, a lower bound of O(20) TeV on the KK scale at leading order is obtained [6,7].…”

“…In our analysis below we carefully analyze the flavour structure of the theory, allowing a rather general bulk Higgs profile. In most of the past studies, the flavour structure of RS was analyzed via the approximation that the Higgs and any relevant KK states are localized on the IR brane, where a transparent spurion structure can be formulated [3]. Here we consider the couplings by calculating full overlap integrals of wavefunctions, and parametrize these corrections by appropriate functions of the form:…”

“…The effective coupling of Q 7 is generated in RS by a loop diagram with a Higgs propagating in the loop [3], as shown in Figure 1. The corresponding Wilson coefficient, evaluated in appendix B, is…”