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We propose a scenario which accommodates all the masses and mixings of the SM fermions in a model of warped extra-dimensions with all matter fields in the bulk. In this scenario, the same flavor symmetric structure is imposed on all the fermions of the Standard Model (SM), including neutrinos. Due to the exponential sensitivity on bulk fermion masses, a small breaking of the symmetry can be greatly enhanced and produce seemingly un-symmetric hierarchical masses and small mixing angles among the charged fermion zero-modes (SM quarks and charged leptons) and wash-out the obvious effects of the symmetry. With the Higgs field leaking into the bulk, and Dirac neutrinos sufficiently localized towards the UV boundary, the neutrino mass hierarchy and flavor structure will still be largely dominated by the fundamental flavor structure. The neutrino sector would then reflect the fundamental flavor structure, whereas the quark sector would probe the effects of the flavor symmetry breaking sector. As an example, we explore these features in the context of a family permutation symmetry imposed in both quark and lepton sectors.
We study the phenomenology of a unified supersymmetric theory with a flavor symmetry $Delta(27)$. The model accommodates quark and lepton masses, mixing angles and CP phases. In this model, the Dirac and Majorana mass matrices have a unified texture zero structure in the $(1,1)$ entry that leads to the Gatto-Sartori-Tonin relation between the Cabibbo angle and ratios of the masses in the quark sectors, and to a natural departure from zero of the $theta_{13}^ell$ angle in the lepton sector. We derive the flavor structures of the trilinears and soft mass matrices, and show their general non-universality. This causes large flavor violating effects. As a consequence, the parameter space for this model is constrained, allowing it to be (dis)proven by flavor violation searches in the next decade. Although the results are model specific, we compare them to previous studies to show similar flavour effects (and associated constraints) are expected in general in supersymmetric flavor models, and may be used to distinguish them.
Here we study the pattern of neutrino oscillations emerging from a previously proposed warped model construction incorporating $Delta(27)$ flavor symmetry. In addition to a complete description of fermion masses, the model predicts the lepton mixing matrix in terms of two parameters. The good measurement of $theta_{13}$ makes these two parameters nearly proportional, leading to an approximate one-parameter description of neutrino oscillations. There is a sharp fourfold degenerate correlation between $delta_{CP}$ and the atmospheric mixing angle $theta_{23}$, so that maximal $theta_{23}$ also implies maximal leptonic CP violation. The predicted electron neutrino and anti-neutrino appearance probabilities indicate that the model should be tested at the T2K, NO$ u$A and DUNE long baseline oscillation experiments.
In extra dimensions, the quark and lepton mass hierarchy can be reproduced from the same order bulk mass parameters, and standard model fermion families can be generated from one generation in the high dimensional space. We try to explain the origin of the same order bulk mass parameters and address the family replication puzzle simultaneously. We show that they correlate with each other. We construct models that families are generated from extra dimensional space, and in the meantime the bulk mass parameters of same order emerge naturally. The interesting point is that the bulk mass parameters, which are in same order, correspond to the eigenvalues of a Schr{o}dinger-like equation. We also discuss the problem existing in this approach.
We show that a discrete exchange symmetry can give rise to realistic dark matter candidates in models with warped extra dimensions. We show how to realize our construction in a variety of models with warped extra dimensions and study in detail a realistic model of Gauge-Higgs Unification/composite Higgs in which the observed amount of dark matter is naturally reproduced. In this model, a realistic pattern of electroweak symmetry breaking typically occurs in a region of parameter space in which the fit to the electroweak precision observables improves, the Higgs is heavier than the experimental bound and new light quark resonances are predicted. We also quantify the fine-tuning of such scenarios, and discuss in which sense Gauge-Higgs Unification models result in a natural theory of electroweak symmetry breaking.
We point out that supersymmetric warped geometry can provide a solution to the SUSY flavor problem, while generating hierarchical Yukawa couplings. In supersymmetric theories in a slice of AdS_5 with the Kaluza-Klein scale M_KK much higher than the weak scale, if all visible fields originate from 5D bulk fields and supersymmetry breaking is mediated by the bulk radion superfield and/or some brane chiral superfields, potentially dangerous soft scalar masses and trilinear $A$ parameters at M_KK can be naturally suppressed compared to the gaugino masses by small warp factor. We present simple models yielding phenomenologically interesting patterns of soft parameters in this framework.