We discuss the implications of assuming a four-zero Yukawa texture for the charged Higgs decay $H^+ \to W^+ γ$ at one-loop level, within the context of the general 2-Higgs Doublet Model of Type III. We begin by presenting a detailed analysis of the charged Higgs boson couplings with heavy quarks and the resulting effects on its decays. In particular, we present the possible enhancement of the decay $H^+ \to W^+ γ$, whose branching ratio could be of the order $\sim 10^{-1}$, for charged Higgs mass of the order 180 GeV. These parameters can still avoid the $B \to X_s γ$ constraint and the perturbativity bound. The production of charged Higgs bosons is also sensitive to the modifications of its couplings, and we evaluate the events rates at the LHC, including the `direct' $c\bar{b}\to H^++c. c.$ and `indirect' $q\bar q, gg \to \bar t b H^++c. c.$ production channels. We get an event rate of order 60 (120) for `direct' (`indirect') production reaction, and including decay $H^+ \to W^+ γ$ in the final state, with an integrated luminosity of $10^5$ $pb^{-1}$.
We show how with an anomaly-free U(1), simple assumptions concerning the origin of Yukawa textures and the Higgs mu-term lead to the prediction of a new physics scale of 10^8GeV and automatic conservation of baryon number.
We point out that New Physics can play an important r\^ ole in rescuing some of the Yukawa texture zero ans\" atze which would otherwise be eliminated by the recent, more precise measurements of $V_{CKM}$. As an example, a detailed analysis of a four texture zero ansatz is presented, showing how the presence of an isosinglet vector-like quark which mixes with standard quarks, can render viable this Yukawa texture. The crucial point is the nondecoupling of the effects of the isosinglet quark, even for arbitrary large values of its mass.
We discuss the origin of Yukawa textures in the string-inspired and string derived models based on the gauge group SU(4)xSU(2)_LxSU(2)_R supplemented by a U(1)_X gauged family symmetry. The gauge symmetries are broken down to those of the minimal supersymmetric standard model which is the effective theory below 10^16 GeV. The combination of the U(1)_X family symmetry and the Pati-Salam gauge group leads to a successful and predictive set of Yukawa textures involving two kinds of texture zeroes: horizontal and vertical texture zeroes. We discuss both symmetric and non-symmetric textures in mode…
We present a detailed analysis of how a mixed-anomaly-free U(1) symmetry can be used to both resolve the slepton mass problem associated with Anomaly Mediated Supersymmetry Breaking and generate the fermion mass hierarchy via the Froggatt-Nielsen mechanism. Flavour changing neutral currents problems are evaded by a specific form of the Yukawa textures.
Talk based on work entitled ``Yukawa textures, new physics and nondecoupling,'' done in collaboration with G. C. Branco and J. I. Silva-Marcos, arXiv:hep-ph/0612252, to appear in Phys. Rev. D. In this work we pointed out that New Physics can play an important r\^ ole in rescuing some of the Yukawa texture zero ans\" atze which would otherwise be eliminated by the recent, more precise measurements of $V_{CKM}$. We have shown that the presence of an isosinglet vector-like quark which mixes with standard quarks, can render viable a particularly interesting four texture zero Yukawa ansatz. The cru…
Four is the maximum number of texture zeros allowed in the Yukawa coupling matrix of three massive neutrinos. These completely fix the high scale CP violation needed for leptogenesis in terms of that accessible at laboratory energies. $μτ$ symmetry drastically reduces such allowed textures. Only one form of the light neutrinos mass matrix survives comfortably while another is marginally allowed.
We analyze the scalar lepton mass matrices in a supersymmetric SO(10) grand unified model with soft SUSY breaking terms generated at Planck scale and a Georgi-Jarslkog Yukawa texture at GUT scale induced by higher dimensional operators. This model predicts lepton flavor violation. The predictive features of the Georgi-Jarlskog texture are used to estimate branching ratios for the radiative decays $e_{a} \rightarrow e_{b}+γ,$ and we find rates that could provide an experimental test for this kind of model.
We discuss possible parallel textures of the Yukawa coupling matrices in the generaltwo-Higgs-doublet model (2HDM). In those textures the flavor changing neutral currentsare naturally suppressed. Motivated by a phenomenologically successful texturewith four texture zeros in the standard model, we propose a predictive ansatz for the Yukawa coupling matrices with the same texture in the general 2HDM. Compared with the six texture-zero based ansatz proposed by Cheng and Sher, it is in a better agreement with the data of quark mixings and CP violation. The four texture-zero based ansatz predicts a…
We consider a restricted Type-I seesaw scenario with four texture zeros in the neutrino Yukawa matrix, in the weak basis where both the charged-lepton Yukawa matrix and the Majorana mass matrix for right-handed neutrinos are diagonal and real. Inspired by grand unified theories, we further require the neutrino Yukawa matrix to exhibit a similar hierarchical pattern to that in the up-type quark Yukawa matrix. With such a hierarchy requirement, we find that leptogenesis, which would operate in a $N_2^{}$-dominated scenario with the asymmetry generated by the next-to-lightest right-handed neutrin…
We emphasize the crucial r\^ ole played by non-factorizable phases in the analysis of the Yukawa flavour structure performed in weak bases with Hermitian mass matrices and with vanishing $(1,1)$ entries. We show that non-factorizable phases are important in order to generate a sufficiently large $\sin 2 β$. A method is suggested to reconstruct the flavour structure of Yukawa couplings from input experimental data both in this Hermitian basis and in a non-Hermitian basis with a maximal number of texture zeros. The corresponding Froggatt--Nielsen patterns are presented in both cases.
Aiming to relate leptonic CP violating phase $δ$ to the cosmological CP asymmetry, we study the extension of MSSM by two quasi-degenerate (strictly degenerate at tree level) right-handed neutrinos and consider all possible two texture zero 3x2 Yukawa matrices plus one $ΔL=2$ dimension five (d=5) operator contributing to the light neutrino mass matrix. We classify all experimentally viable mass matrices, leading to several predictions, and analytically derive predictive relations. We also relate the CP violating $δ$ phase to the CP phase of the thermal leptogenesis.
Within the type-I seesaw and in the basis where charged lepton and heavy neutrino mass matrices are real and diagonal, $μτ$ symmetric four and three zero neutrino Yukawa textures are perturbed by lowest order $μτ$ symmetry breaking terms. These perturbations are taken to be the {\it most general ones for those textures}. For quite small values of those symmetry breaking parameters, permitting a lowest order analysis, current best-fit ranges of neutrino mass squared differences and mixing angles are shown to be accommodable, including a value of $θ_{13}$ in the observed range, provided all the …
We show that a large class of sets of leptonic texture zeros considered in the literature imply the vanishing of certain CP-odd weak-basis invariants. These invariant conditions enable one to recognize a flavour model corresponding to a set of texture zeros, when written in an arbitrary weak-basis where the zeros are not manifest. We also analyse the r\^ ole of texture zeros in allowing for a connection between leptogenesis and low-energy leptonic masses, mixing and CP violation. For some of the textures the variables relevant for leptogenesis can be fully determined in terms of low energy par…
As the first topic, we propose a new parametrization of the complex Yukawa matrix in the scotogenic model. The new parametrization is compatible with the particle data group parametrization of the neutrino sector. Some analytical expressions for the neutrino masses with the new parametrization are shown. As the second topic, we consider the phenomenology of the socotogenic model with the one-zero-textures of the neutrino flavor mass matrix. One of the six patterns of the neutrino mass matrix is favorable for the real Yukawa matrix. On the other hand, for the complex Yukawa matrix, five of the …
We investigate 'Scaling ansatz' in the neutrino sector within the framework of type I seesaw mechanism with diagonal charged lepton and right handed Majorana neutrino mass matrices ($M_R$). We also assume four zero texture of Dirac neutrino mass matrices ($m_D$) which severely constrain the phenomenological outcomes of such scheme. Scaling ansatz and the present neutrino data allow only Six such matrices out of 126 four zero Yukawa matrices. In this scheme, in order to generate large $θ_{13}$ we break scaling ansatz in $m_D$ through a perturbation parameter and we also show our breaking scheme…
We explore, in the MSSM context, an extension of the Anomaly Mediated Supersymmetry Breaking solution for the soft scalar masses that is possible if the underlying theory has a gauged R-symmetry. The slepton mass problem characteristic of the scenario is resolved, and a context for the explanation of the fermion mass hierarchy provided.
The scotogenic model is well known for accommodating small neutrino mass and dark matter. Here, we have realized the scotogenic model with the help of discrete flavor symmetry $A_{4}\otimes Z_{4}$. We have obtained three one zero textures of Yukawa coupling matrices from the model and have studied its impact on neutrino phenomenology and related aspects of cosmology. On the basis of $μ-τ$ symmetry, we have further discarded two structures of one zero texture Yukawa coupling matrix. We further analyze if the effective mass of active neutrinos obtained by the virtue of the Yukawa coupling matrix…
Assuming a diagonal Majorana neutrino mass matrix, we investigate the neutrino Yukawa textures which lead to a non-zero reactor mixing angle $θ_{13}$. The neutrino effective coupling matrix $κ^{eff}$ is pre-diagonalized by a constant mixing pattern $V_ν$ with a vanishing $θ^ν_{13}$. The resulting pre-diagonal symmetrical matrix $κ$ is set to be four texture zeros with two types of off-diagonal elements nonzero, which is $κ_{13}$ and $κ_{23}$, respectively. With the expectation of simple textures we thoroughly classify the linear combinations, $α_{i}$, $β_{i}$ and $γ_{i}$ of Yukawa elements $λ_…
The Two Higgs Doublets Model (2HDM) has provided a very useful way to describe a minimal extension of the scalar sector of the Standard Model. In this work, it is shown a scheme that we call Partial Aligned Two Higgs Doublet Model (PA-2HDM) which allows a description of the distinct versions of the 2HDM in a simple way, including those with flavor symmetries. In addition, it is shown a method to diagonalize Yukawa matrices of four-zero texture coming from the 2HDM-III. We provide some phenomenological applications in order to show the model's predictive power.
The quark mass matrices ansatze proposed by Fritzsch, Du-Xing and Fukuyama-Nishiura in the framework of the general two Higgs doublet model are studied. The corresponding Yukawa matrices in the flavor basis in the different cases considered are discussed. The corresponding Cabbibo-Kobayashi-Maskawa matrix elements are computed in all cases and compared with their experimental values. The complex phases of the ansatze are taken into account and the CP violating phase $δ$ is computed. Finally, in order to observe the influence of the different kind of textures of Yukawa coupling matrices conside…
We study a set of textures giving rise to correct masses and mixings of the charged fermions in the context of leptogenesis. The Dirac neutrino texture pattern is assumed to be identical with the up quark texture. The heavy Majonana neutrino mass matrix is obtained by inverting the type-I see-saw formula and using the neutrino masses and mixings required by the solar and atmospheric neutrino oscillation experiments as input. After making the feasibility study of the generated lepton asymmetry via the decay of the heavy right handed neutrino, we compute the generated baryon asymmetry by numeric…
In a SUSY GUT model responsible for generating symmetric quark mass matrices at the GUT scale (mu = Lamda) we assume that the top-Yukawa coupling, lamda_t, becomes infinite at that scale. As a consequence, the MSSM renormalization group equations for quark Yukawa couplings exhibit hierarchical solutions which lead to a pattern of texture zeroes in quark mass matrices at mu = Lamda similar to one of the solutions of Ramond, Roberts, and Ross. The evolution in energy scale to low energies shows excellent agreement between the measured quantities involving the scale-independent ratios of CKM matr…
We investigate, within the Type I seesaw framework, the physical implications of zero textures in the Yukawa couplings which generate the neutrino Dirac mass matrix $m_D$. It is shown that four is the maximal number of texture zeroes compatible with the observed leptonic mixing and the assumption that no neutrino mass vanishes. We classify all allowed four-zero textures of $m_D$ into two categories with three classes each. We show that the different classes, in general, admit CP violation both at low and high energies. We further present the constraints obtained for low energy physics in each …
Integration of superpartners out of the spectrum induces potentially large contributions to Yukawa couplings. These corrections, the supersymmetric threshold corrections, therefore influence the CKM matrix prediction in a non-trivial way. We study effects of threshold corrections on high-scale flavor structures specified at the gauge coupling unification scale in supersymmetry. In our analysis, we first consider high-scale Yukawa textures which qualify phenomenologically viable at tree level, and find that they get completely disqualified after incorporating the threshold corrections. Next, we…
The arbitrariness of Yukawa couplings can be reduced by the imposition of some flavor symmetries and/or by the realization of texture zeros. We review neutrino Yukawa textures with zeros within the framework of the type-I seesaw with three heavy right chiral neutrinos and in the basis where the latter and the charged leptons are mass diagonal. An assumed non-vanishing mass of every ultralight neutrino and the observed non-decoupling of any neutrino generation allow a maximum of four zeros in the Yukawa coupling matrix $Y_ν$ in family space. There are seventy two such textures. We show that the…
The observed hierarchy of the quark and lepton masses and mixing angles has led to the parametrisation of the mass matrices in powers of the Cabibbo angle and a certain number of zeros. The origin of these ``textures'' may lie in symmetries present at the GUT/string unification scale. We discuss the case of an extra $U(1)$. Symmetric textures with two or three zeros can be generated through high-order operators containing light/heavy Higgs multiplets and singlet fields. However, a realistic scenario for generating both the up- and down-quark mass matrices is not possible within the MSSM with a…
The observed hierarchy of quark and lepton masses and mixings may be obtained by adding an abelian family symmetry to the Minimal Supersymmetric Model and coupling quarks and leptons to an electroweak singlet scalar field. In a large class of such models, this symmetry suffers from anomalies which must be compensated by the Green-Schwarz mechanism; this in turn fixes the electroweak mixing angle to be $\sin^2 θ_W = 3/8$ at the string scale, without any assumed GUT structure. The analysis is extended to two distinct generalisations of the Standard Model: neutrino masses and mixings and R-parity…
\noindent We revisit the \textit{minimal seesaw model}, i.e., the type-I seesaw mechanism involving only two right-handed neutrinos. % This model represents an important minimal benchmark scenario for future experimental updates on neutrino oscillations. % It features four real parameters that cannot be fixed by the current data: two $CP$-violating phases, $δ$ and $σ$, as well as one complex parameter, $z$, that is experimentally inaccessible at low energies. % The parameter $z$ controls the structure of the neutrino Yukawa matrix at high energies, which is why it may be regarded as a label or…
We augment the Minimal Supersymmetric Standard Model with a gauged family-dependent $U(1)$ to reproduce Yukawa textures compatible with experiment. In the simplest model with one extra chiral electroweak singlet field, acceptable textures require this $U(1)$ to be anomalous. The cancellation of its anomalies by a generic Green-Schwarz mechanism requires $\sin^2θ_w=3/8$ at the string scale, suggesting a superstring origin for the standard model.
We study flavor violating processes in the production or decay of a neutral pseudoscalar meson $P^0$ in the framework of a general two Higgs Doublet Model type III (2HDM-III). We use a version of the model where Yukawa interactions of neutral Higgs bosons allow for flavor change at the tree-level, but conserves CP symmetry. We focus on all possible $τ^{\pm} \to l^{\pm}P^0 $ and $P^0 \to l^+l'^-$ decay channels, where $l,l'$ are charged leptons. We find that these processes provide complementary information on quark and lepton FCNC Yukawa couplings. In particular flavor violating parameters in …
In this letter we analyse, in the context of the general 2-Higgs Doublet Model, the structure of the Yukawa matrices, $\widetilde{ \bf Y}_{ _{1,2} }^{q}$, by assuming a four-zero texture ansatz for their definition. In this framework, we obtain compact expressions for $\widetilde{ \bf Y}_{ _{1,2} }^{q}$, which are reduced to the Cheng and Sher ansatz with the difference that they are obtained naturally as a direct consequence of the invariants of the fermion mass matrices. Furthermore, in order to avoid large flavour violating effects coming from charged Higgs exchange, we consider the main fl…
The effect of $Z_3$ symmetry on the general Two Higgs Doublet Model is explored. Of particular interest is the question of what can a $Z_3$ symmetry do beyond the usual case with $Z_2$. There are two independent scenarios that give some interesting results: first, by giving non-trivial charges to the Standard Model fermions, it is possible to use the $Z_3$ symmetry of the scalar potential to generate potentially useful Yukawa textures. This is not possible with $Z_2$. A series of possibilities is presented where their viability is addressed and a specific example in the quark sector is given f…
In this letter, we show how the combination of both a gauged U(1)_X family symmetry and an extended vertical gauge symmetry in a single model, allows for the presence of additional Clebsch texture zeroes in the fermion mass matrices. This leads to new structures for the textures, with increased predictivity, as compared to schemes with enhanced family symmetries only. We illustrate these ideas in the context of the Pati-Salam gauge group SU(4)xSU(2)_LxSU(2)_R$ supplemented by a U(1)_X gauged family symmetry. In the case of symmetric mass matrices, two of the solutions of Ramond, Roberts and Ro…
We study quark mass matrices derived from magnetized $T^2/\mathbb{Z}_2$ orbifold models. Yukawa matrices at three modular fixed points, $τ=i, e^{2πi/3}$ and $i\infty$ are invariant under $S$, $ST$ and $T$-transformations. We study these invariances on $T^2/\mathbb{Z}_2$ twisted orbifold. We find that Yukawa matrices have a kind of texture structures although ones at $τ=i\infty$ are not realistic. We classify Yukawa textures at $τ=i$ and $e^{2πi/3}$. Moreover we investigate the conditions such that quark mass matrix constructed by Yukawa textures becomes approximately rank one matrix, which is …
For type I seesaw and in the basis where the charged lepton and heavy right-handed neutrino mass matrices are real and diagonal, four has been shown to be the maximum number of zeros allowed in the neutrino Yukawa coupling matrix $Y_ν$. These four zero textures have been classified into two distinct categories. We investigate certain phenomenological consequences of these textures within a supersymmetric framework. This is done by using conditions implied on elements of the neutrino Majorana mass matrix for textures of each category in $Y_ν$. These conditions turn out to be stable under radiat…
Maximally Symmetric $n$-Higgs Doublet Models (MS-$n$HDMs)define very economic settings that enable sharp Higgs-sector predictions beyond the Standard Model (SM) potentially testable at high-energy colliders. The scalar potential of a MS-$n$HDM obeys an $\mathrm{Sp(2}n)$ symmetry, which is softly broken by bilinear scalar masses and explicitly by hypercharge and Yukawa couplings through renormalisation-group effects. The $\mathrm{Sp(2}n)$ also ensures natural SM alignment and allows for quartic coupling unification up to the Planck scale. As typical examples, we consider maximally symmetric rea…
With the recent observation of nonzero θ_{13}, five neutrino oscillation parameters are now known. By imposing four zeros in the Yukawa coupling matrix of the type I seesaw model, the number of parameters in the neutrino mass matrix is reduced to seven, and we are able to make predictions for the lightest neutrino mass, Dirac CP phase, and neutrinoless double beta decay. Four texture zeros in the Yukawa coupling matrix is equivalent to either a single texture zero or a single cofactor zero for an off-diagonal element of the light neutrino mass matrix. We find strong similarities between single…
We develop a systematic analysis of quark mass matrices which, starting with the measured values of quark masses and mixing angles, allows for a model independent search for all possible (symmetric or hermitian) mass matrices having texture zeroes at the unification scale. A survey of all six and five texture zero structures yields a total of five possible solutions which may be distinguished by improved measurements of the CKM matrix elements and which may readily be extended to include lepton masses with the Georgi-Jarlskog texture. The solutions naturally suggest a parameterisation for the …
Within the type-I seesaw framework with three heavy right chiral neutrinos and in the basis where the latter and the charged leptons are mass diagonal, a near `mu-tau' symmetry in the neutrino sector is strongly suggested by the neutrino oscillation data. There is further evidence for a close to the tribimaximal mixing pattern which subsumes `mu-tau' symmetry. On the other hand, the assumption of a (maximally allowed) four zero texture in the Yukawa coupling matrix Y_nu in the same basis leads to a highly constrained and predictive theoretical scheme. We show that the requirement of an exact `…
We discuss the implications of assuming a four-zero Yukawa texture for the properties of the charged Higgs boson within the context of the general 2-Higgs Doublet Model of Type III. We present the charged Higgs boson couplings with heavy quarks and the resulting pattern for its decays, including the decay $H^+ \to W^+ γ$ at 1-loop level. The parameters chosen can still avoid the $B \to X_s γ$ constraint, the perturbativity and $ρ_0$ bound. Also, we present the constraints of $ B0-\bar{B}0$ mixing and of the radiative corrections to the $Z b \bar{b}$ vertex in the regime small $ \tan β$. The pr…
We examine the structure of the Yukawa couplings in the 11 dimensional Horava-Witten M-theory based on non-standard embeddings. We find that the CKM and quark mass hierarchies can be explained in M Theory without introducing undue fine tuning. A phenomenological example is presented satisfying all CKM and quark mass data requiring the 5-branes cluster near the second orbifold plane, and that the instanton charges of the physical orbifold plane vanish. The latter condition is explicitly realized on a Calabi-Yau manifold with del Pezzo base dP_7.
Four zero neutrino Yukawa textures in a specified weak basis, combined with $μτ$ symmetry and type-I seesaw, yield a highly constrained and predictive scheme. Two alternately viable $3\times3$ light neutrino Majorana mass matrices $m_{νA}/m_{νB}$ result with inverted/normal mass ordering. Neutrino masses, Majorana in character and predicted within definite ranges with laboratory and cosmological inputs, will have their sum probed cosmologically. The rate for $0νββ$ decay, though generally below the reach of planned experiments, could approach it in some parameter region. Departure from $μτ$ sy…
We discuss flavor-violating constraints and consequently possible charged Higgs boson phenomenology emerging from a four-zero Yukawa texture embedded within the Type-III 2-Higgs Doublet Model (2HDM-III). Firstly, we show in detail how we can obtain several kinds of 2HDMs when some parameters in the Yukawa texture are absent. Secondly, we present a comprehensive study of the main B-physics constraints on such parameters induced by flavor-changing processes, in particular on the off-diagonal terms of such a texture: i.e., from $μ-e$ universality in $τ$ decays, several leptonic B-decays ($B \to τ…
In a Partially Aligned Two Higgs Doublet Model, where only is allowed flavor violation between third and second generation of fermions, we propose a mechanism to generate the second Yukawa matrix through a Unitary V-Spin flavor transformation on the mass matrix for quarks and leptons. Also we assume that this flavor transformation is universal, this is, we use the same parameters to generate Yukawa matrix elements in both sectors, reducing drastically the number of free parameters. As consequence we obtained a serie of relations between Yukawa matrix elements, that we called the Universality C…
I present an algorithm in the search for symmetric textures in the quark Yukawa matrices. This is based on a talk at the Coral Gables conference in January 1993. I include the macro tables2.tex for making tables, and use the Santa Barbara jnl and reforder macros.
We update the flavor-violating constraints on the charged Higgs sector of the 2-Higgs Doublet Model Type-III (2HDM-III), using a four-zero texture in the Yukawa matrices. We give a generic Lagrangian of the 2HDM-III. In order to show the relevance of the off-diagonal terms of such a texture, we utilize the main constraints from $B$-physics, $μ-e$ universality in $τ$ decays and the radiative decay $Z\to b \bar{b}$ presented recently in arXiv:1212.6818 [hep-ph]. In particular, we show that the $H^- c \bar{b}$ coupling can be very large and very different with respect to 2HDMs with a flavor discr…
All quark mass matrices with texture zeroes obtained through weak basis transformations are confronted with the experimental data. The reconstruction of the quark mass matrices M_u and M_d at the electroweak scale is performed in a weak basis where the matrices are Hermitian and have a maximum of three vanishing elements. The same procedure is also accomplished for the Yukawa coupling matrices at the grand unification scale in the context of the Standard Model and its minimal supersymmetric extension as well as of the two Higgs doublet model. The analysis of all viable power structures on the …
We study the substantial enhancement, with respect to the corresponding Standard Model rates, that can be obtained for the branching ratios of the decay channels $h \to γγ$ and $h\to γZ$ within the framework of the Two Higgs Doublet Model Type III, assuming a four-zero Yukawa texture and a general Higgs potential. We show that these processes are very sensitive to the flavor pattern entering the Yukawa texture and to the triple coupling structure of the Higgs potential, both of which impact onto the aforementioned decays. We can accommodate the parameters of the model in such a way to obtain t…
We implement a symmetry violation guideline into a two-Higgs-doublet model embedded with three right-handed neutrinos, and exploit the generic Yukawa structures of the model via a hypothetical symmetry restoration of a global $U_Q(1)^3\times U_L(1)^3$ symmetry. We then apply a mass-powered parametrization to construct the phenomenologically motivated Yukawa interactions, which enables us to incorporate correlatively the neutrino mass, dark matter, as well as the lepton-flavor universality violations in $R_{K^{(*)}}$ and $R_{D^{(*)}}$. Specifically, two atmospheric-scale neutrino masses are gen…
Within the low scale resonant leptogenesis scenario, the cosmological CP asymmetry may arise by radiative corrections through the charged lepton Yukawa couplings. While in some cases, as one expects, decisive role is played by the $λ_{τ}$ coupling, we show that in specific neutrino textures only by inclusion of the $λ_{μ}$ the cosmological CP violation is generated at 1-loop level. With the purpose to relate the cosmological CP violation to the leptonic CP phase $δ$, we consider an extension of MSSM with two right handed neutrinos (RHN), which are degenerate in mass at high scales. Together wi…
The generation of the right amount of baryon asymmetry $η$ of the Universe from supersymmetric leptogenesis is studied within the type-I seesaw framework with three heavy singlet Majorana neutrinos $N_i\,\,(i = 1,2,3)$ and their superpartners. We assume the occurrence of four zeroes in the neutrino Yukawa coupling matrix $Y_ν$, taken to be $μτ$ symmetric, in the weak basis where $N_i$ (with real masses $M_i>0$) and the charged leptons $l_α\,\, (α= e,μ,τ)$ are mass diagonal. The quadrant of the single nontrivial phase, allowed in the corresponding light neutrino mass matrix $m_ν$, gets fixed an…
We present a model of fermion masses based on a minimal, non-Abelian discrete symmetry that reproduces the Yukawa matrices usually associated with U(2) theories of flavor. Mass and mixing angle relations that follow from the simple form of the quark and charged lepton Yukawa textures are therefore common to both theories. We show that the differing representation structure of our horizontal symmetry allows for new solutions to the solar and atmospheric neutrino problems that do not involve modification of the original charged fermion Yukawa textures, or the introduction of sterile neutrinos.
We examine the flavor structure of the trilinear superpotential couplings which can result from embedding the Standard Model within D brane sectors in Type IIB orientifold models, which are examples within the Type I string framework. We find in general that the allowed flavor structures of the Yukawa coupling matrices to leading order are given by basic variations on the "democratic" texture ansatz. In certain interesting cases, the Yukawa couplings have a novel structure in which a single right-handed fermion couples democratically at leading order to three left-handed fermions. We discuss t…
Recent advances in 11 dimensional Horava-Witten M-theory based on non-standard embeddings with torus fibered Calabi-Yau manifolds have allowed the construction of three generation models with Wilson line breaking to the Standard Model gauge symmetry. Central to these constructions is the existence of a set of 5-branes in the bulk. We examine within this framework the general structure of the matter Yukawa couplings and show that M-theory offers an alternate possible way of achieving the CKM and quark mass hierarchies without introducing undue fine tuning or (as in conventional analysis) small …
