We show that most features of the mass and mixing pattern of the second and third SM fermion families can be accounted for without making use of flavour symmetries or other types of flavour dynamics. We discuss the implications for flavour phenomenology, in particular for the $τ\toμγ$ decay rate, and comment on LFV effects at colliders. We show that the model can be embedded in a full SO(10) supersymmetric GUT in 5 dimensions that preserves the successful MSSM gauge coupling unification prediction for $α_s$. Interesting features of this embedding are i) the connection of one of the hierarchy parameters with the strong coupling assumption, ii) the absence of KK threshold effects on the $α_s$ prediction at one loop, and iii) the shift of the GUT scale up to about $10^{17}\GeV$. Proton decay is under control, also due to the larger GUT scale. A large atmospheric angle for normal hierarchical neutrinos is obtained in an unusual way.
We provide a complete answer to the following question: what are the flavour groups and representations providing, in the symmetric limit, an approximate description of lepton masses and mixings? We assume that neutrinos masses are described by the Weinberg operator. We show that the pattern of lepton masses and mixings only depends on the dimension, type (real, pseudoreal, complex), and equivalence of the irreducible components of the flavour representation, and we find only six viable cases. In all cases the neutrinos are either anarchical or have an inverted hierarchical spectrum. In the co…
The masses of the charged fermion and the mixing angles among quarks are observed to be strongly hierarchical, while analogous parameters in the neutrino sector appear to be structure-less or anarchical. We develop a class of unified models based on SU(5) symmetry that explains these differing features probabilistically. With the aid of three input parameters that are hierarchical, and with the assumption that all the Yukawa couplings are uncorrelated random variables described by Gaussian distributions, we show by Monte Carlo simulations that the observed features of the entire fermion spectr…
Model independent analysis of the simultaneous mixing of gauge bosons and mixing of fermions
我们讨论的情况下，同时混合的规范玻色子和混合的费米子在一个模型独立的方式和各种额外的费米子表示。本文分析了一类轻子族违反过程，即在存在一个额外的中性规范玻色子Z '的情况下，具有普适、非普适或族变耦合的轻子族违反过程Z --> etau，Z--> mu，Z --> e mu，mu--> e e e，tau--> e e e e，tau --> mu mu，tau --> e mu mu和tau --> mu e e.我们导出了Z-Z'混合和普通-奇异轻子混合的联合效应的界。
I propose the first multiscalar singlet extension of the Standard Model (SM), that generates tree level top quark and exotic fermion masses as well as one and three loop level masses for charged fermions lighter than the top quark and for light active neutrinos, respectively, without invoking electrically charged scalar fields. That model, which is based on the $S_{3}\times Z_{8}$ discrete symmetry, successfully explains the observed SM fermion mass and mixing pattern. The charged exotic fermions induce one loop level masses for charged fermions lighter than the top quark. The $Z_{8}$ charged …
We propose a predictive inert 2 Higgs doublet model, where the Standard Model (SM) symmetry is extended by $S_{3}\otimes Z_{2}\otimes Z_{12}$ and the field content is enlarged by extra scalar fields, charged exotic fermions and two heavy right-handed Majorana neutrinos. The charged exotic fermions generate a nontrivial quark mixing and provide one-loop-level masses for the first- and second-generation charged fermions. The masses of the light active neutrinos are generated from a one loop-level radiative seesaw mechanism. Our model successfully explains the observed SM fermion mass and mixing …
We propose a multiscalar singlet extension of the singlet-triplet Higgs model capable of explaining the SM fermion mass spectrum and mixing parameters. Our model is based on the $Δ\left( 27\right) $ family symmetry, supplemented by cyclic symmetries, which are spontaneously broken thus yielding the observed hierarchy of the SM charged fermion masses and quark mixing angles. The masses of the light active neutrinos are produced by type-II seesaw mechanism mediated by the neutral component of the $SU(2)_{L}$ scalar triplet. The model symmetries lead to the extended Gatto-Sartori-Tonin relations …
We consider a flavor model based on A4 modular group to account for both lepton and quark parameters (masses and mixing). The inverse seesaw mechanism is considered to produce the light neutrino masses. Lepton masses and mixing are obtained in terms of Yukawa coupling ratios and values of the modulus τ nearby some fixed points for inverted neutrino mass hierarchy. The quark masses and mixing are arisen at the same τ values used in inverted neutrino mass hierarchy and are in agreements with the recent data.
We propose that the radiative generation of the neutrino mass can be achieved by incorporating the kinetic mixing of fermion fields which arises radiatively at one-loop level. As a demonstrative example of the application of the mechanism, we present the particular case of the Standard Model extension by $U(1)_D$ symmetry. As a result, we show how neutrino masses can be generated via a kinetic mixing portal instead of a mass matrix with residual symmetries responsible for the stability of multicomponent dark matter.
331 vector-like models with mirror fermions as a possible solution for the discrepancy in the b-quark asymmetries, and for the neutrino mass and mixing pattern
Flavor transitions via the charged current interactions are parametrized by a three dimensional and unitary transformation. This so called mixing matrix requires of four mixing parameters. Here we show that under the phenomenological observation of hierarchical fermion masses, $m_3 \gg m_2 \gg m_1$, a mixing parametrization can be built with its mixing parameters being the corresponding four independent mass ratios of each fermion sector, i.e., $m_u/m_c$, $m_c/m_t$, $m_d/m_s$, and $m_s/m_b$ and $m_e/m_μ$, $m_μ/m_τ$, $m_{ν1}/m_{ν2}$, and $m_{ν 2}/m_{ν3}$, for the quark and lepton sector, respec…
