We present the electroweak and flavour structure of a model with a warped extra dimension and the bulk gauge group SU (3) c × SU (2) L × SU (2) R × P LR × 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.

We perform a detailed analysis of the SO(10) SUSY GUT model with D 3 family symmetry of Dermíšek and Raby (DR). The model is specified in terms of 24 parameters and predicts, as a function of them, the whole MSSM set of parameters at low energy scales. Concerning the SM subset of such parameters, the model is able to give a satisfactory description of the quark and lepton masses, of the PMNS matrix and of the CKM matrix. We perform a global fit to the model, including flavour changing neutral current (FCNC) processes B s → µ + µ − , B → X s γ, B → X s ℓ + ℓ − and the B d,s − B d,s mass differences ∆M d,s as well as the flavour changing (FC) process B + → τ + ν. These observables provide at present the most sensitive probe of the SUSY mass spectrum and couplings predicted by the model. Our analysis demonstrates that the simultaneous description of the FC observables in question represents a serious challenge for the DR model, unless the masses of the scalars are moved to regions which are problematic from the point of view of naturalness and probably beyond the reach of the LHC. We emphasize that this problem could be a general feature of SUSY GUT models with third generation Yukawa unification and weak-scale minimal flavour violation.

The Flavour Symmetry of the Standard Model (SM) gauge sector is broken by the fermion Yukawa couplings. Promoting the Yukawa matrices to scalar spurion fields, one can break the flavour symmetry spontaneously by giving appropriate vacuum expectation values (VEVs) to the spurion fields. In addition, one encounters Goldstone modes for every broken flavour symmetry generator. In this paper, we discuss the implications of interpreting these Goldstone modes as longitudinal modes for massive gauge bosons of a local flavour symmetry. Because of the chiral nature of the SM flavour symmetry, we encounter gauge anomalies which can be consistently treated within an effective-field theory framework. On the other hand, leaving the U (1) factors of the flavour symmetry group as global symmetries, the respective Goldstone modes behave as axions which can be used to resolve the strong CP problem by a modified Peccei-Quinn mechanism. In this dynamical picture of flavour symmetry breaking, one encounters new sources of flavour-changing neutral currents, which arise from integrating out heavy scalar spurion fields and heavy gauge bosons. The coefficients of the effective operators follow the minimal-flavour violation principle.