We study leptonic CP and flavor violations in supersymmetric (SUSY) grand unified theory (GUT) with right handed neutrinos, paying attention to the renormalization group effects on the slepton mass matrices due to the neutrino and GUT Yukawa interactions. In particular, we study in detail the impacts of the so-called Casas- Ibarra parameters on CP and flavor violating observables. The renormalization group effects induce CP and flavor violating elements of the SUSY breaking scalar mass squared matrices, which may result in sizable leptonic CP and flavor violating signals. Assuming seesaw formula for the active neutrino masses, the renormalization group effects have been often thought to be negligible as the right-handed neutrino masses become small. With the most general form of the neutrino Yukawa matrix, i.e., taking into account the Casas-Ibarra parameters, however, this is not the case. We found that the maximal possible sizes of signals of leptonic CP and flavor violating processes are found to be insensitive to the mass scale of the right-handed neutrinos and that they are as large as (or larger than) the present experimental bounds irrespective of the right-handed neutrino masses.
The neutrino flavor mixing may induce rich flavor and CP violating phenomena in the SUSY GUTs. In this paper we discuss the hadronic EDMs and the correlation among low-energy processes induced by the mixings between second and third generations in the SUSY SU(5) GUT with the right-handed neutrinos.
CP violation in the B_d system is discussed in the supersymmetric grand unified theory (GUT) with the right-handed neutrinos. Above the GUT scale, the right-handed down-type squarks couple to the right-handed neutrinos. Due to the renormalization group effect, flavor violations in the lepton sector may be transfered to the right-handed down-type squark mass matrix, which affects the CP violation in the B decay. Taking into account this effect, we compare the CP violation in B_d \to ψK_S and B_d \to ϕK_S processes. We will find that a significant difference is possible between the CP violating …
We discuss hadronic EDM constraints on the neutrino sector in the SUSY SU(5) GUT with the right-handed neutrinos. The hadronic EDMs are sensitive to the right-handed down-type squark mixings, especially between the second and third generations and between the first and third ones, compared with the other low-energy observables, and the flavor mixings are induced by the neutrino Yukawa interaction. The current experimental bound of the neutron EDM may imply that the right-handed tau neutrino mass is smaller than about 10^{14} GeV in the minimal supergravity scenario, and it may be improved furt…
The (B_{d}\longrightarrow ΦK_{s}) process is without tree level decay amplitude . Then the SUSY contributions may be significant . We calculate the neutralino and gluino penguin contributions to the CP violating phase in (SU(5) ) grand unified theory with right-handed neutrino (SU(5)_{RN}) . We find that the SUSY contribution may change the phase in (B_{d}\longrightarrow ΦK_{s} ).
We obtain a phenomenologically acceptable PMNS matrix in a flipped SU(5) model inspired by the compactification of heterotic string $E_8\times E_8'$. To analyze the Jarlskog determinant efficiently, we include the simple Kim-Seo form for the Pontecorbo-Maki-Nakagawa-Sakata matrix. We also noted that $|δ_{\rm PMNS}|\lesssim 64^{\rm o}$ for the normal hierarchy of neutrino masses with the PDG book parametrization.
It is recently announced by the {\bf Ut}{\it fit} collaboration that the CP phase of the $B_s$ mixing amplitude, $ϕ_{B_s}$, deviates more than $3 σ$ from the standard-model prediction. In this paper we discuss how large correction to $ϕ_{B_s}$ is possible in the supersymmetric SU(5) ground unified model (SUSY SU(5) GUT) with right-handed neutrinos. Here, we assume the supergravity-like boundary condition for the SUSY-breaking terms. We found that the 95% probability region derived by the {\bf Ut}{\it fit} collaboration is marginal in this model.
We examine lepton flavor violating (LFV) interactions for heavy right-handed neutrinos that exist in most of the standard model extensions that address dark matter (DM) and neutrino mass at the loop level. In order to probe the collider effect of these LFV interactions, we impose the assumption that the model parameters give the right values of the DM relic density and fulfill the constraints from the LFV processes $\ell_α\rightarrow\ell_βγ$ and $\ell_α\rightarrow3\ell_β$. We also investigate the possibility of probing these interactions, and hence the right-handed neutrino, at leptonic collid…
We derive renormalization group equations for neutrino masses, leptonic mixing angles and CP-violating phases running at energies above the seesaw threshold, both in the Standard Model and in the Minimal Supersymmetric Standard Model extended with three right-handed neutrinos. With these equations, we carry out a systematic study of the radiative correction that may arise to neutrino parameters, via their renormalization group evolution from the electroweak scale ($M_{\rm Z}$) to the scale of Grand Unified theories ($Λ_{\rm GUT}$). We study in detail three typically interesting neutrino mass p…
We consider a neutrino mass model where all leptonic mixing is induced by a heavy Majorana sector through the seesaw type I mechanism, while the Dirac mass matrices are diagonal. Such a pattern occurs naturally in grand unified theories. Constraints on the parameters of the models are considered and it is shown that a normal neutrino mass hierarchy is preferred. The lightest neutrino mass is typically small, leading to nonobservable rates for neutrinoless double beta decay in the normal hierarchy case.
We analyze possible lepton-flavor-violating decays of the $Z^0$ particle in a minimal extension of the Standard Model, in which one right-handed neutral field for each family has been introduced. Such rare leptonic decays are induced by Majorana neutrinos at the first electroweak loop level and are generally not suppressed by the ordinary "see-saw" mechanism. In particular, we find that experimental bounds on branching ratios of the order of $10^{-5}-10^{-6}$ attainable at $LEP$ may impose constraints on lepton-flavor-mixing parameters and the masses of the heavy Majorana neutrinos.
In the SUSY SU(5) GUT with the right-handed neutrinos, the neutrino Yukawa coupling induces the flavor-violating mass terms for the right-handed down squarks and left-handed sleptons, and they lead to imprint on the flavor physics in the hadronic and leptonic sectors. In this paper we study CP violation in $B_d^0$ and $B_s^0$, which is induced by the tau-neutrino Yukawa coupling. In particular, we notice the correlation of the CP asymmetries in $B_d^0\to ϕK_s$ ($S_{ϕK_s}$) and $B_s^0\to J/ψϕ$ ($S_{J/ψϕ}$) with other observables, such as $Br(τ\toμγ)$, the muon EDM ($d_μ$), and the mixing-induce…
In the SUSY GUT scenario, it is natural to assume the right-handed-neutrino Majorana-mass scale to be $10^{16}$ GeV. This will in principle lead, by the seesaw mechanism, to a $ ν_τ $ mass of order $ m_t^2 / (10^{16}\, {\rm GeV}) \sim 3 \times 10^{-3}\, {\rm eV} $. This suggests that the solution of the solar-neutrino puzzle should be either the MSW effect in $ν_e$--$ν_τ$ oscillations, with $ m_{ν_τ}^2 \sim 10^{-5}\, {\rm eV}^2 $, or long-wavelength $ν_e$--$ν_μ$ oscillations, with $ m_{ν_μ}^2 \sim 10^{-10}\, {\rm eV}^2 $. These solutions require unexpectedly large mixings of $ ν_e $ with $ ν_τ…
Many GUT models conserve the difference between the baryon and lepton number, $B-L$. These models can create baryon and lepton asymmetries from heavy Higgs or gauge boson decays with $B+L \neq 0$ but with $B-L=0$. Since the sphaleron processes violate $B+L$, such GUT-generated asymmetries will finally be washed out completely, making GUT baryogenesis scenarios incapable of reproducing the observed baryon asymmetry of the Universe. In this work, we revisit the idea to revive GUT baryogenesis, proposed by Fukugita and Yanagida, where right-handed neutrinos erase the lepton asymmetry before the s…
We consider a situation where right-handed neutrinos couple to a light scalar which is possibly a Nambu-Goldstone boson resulting from high-energy symmetry breaking. Its coupling is typically complex-valued and flavor-dependent. In this work, we investigate the possibility of the leptonic asymmetry generation in the Universe from the right-handed neutrino decay to flavorful light scalar. Furthermore a new source of asymmetry generation from a single decay process is pointed out, which is characteristic of the present setting.
We study the thermal leptogenesis in the $E_6\times U(1)_A$ SUSY GUT model in which realistic masses and mixings of quarks and leptons can be realized. We show that the sufficient baryon number can be produced by the leptogenesis in the model, in which the mass parameter of the lightest right-handed neutrino is predicted to be smaller than $10^8$ GeV. The essential point is that the mass of the lightest right-handed neutrino can be enhanced in the model because it has a lot of mass terms whose mass parameters are predicted to be the same order of magnitude which is smaller than $10^8$ GeV. We …
Alternative renormalizable minimal non-SUSY SO(10) GUT model is proposed. Instead of a ${\bf 126}$-dimensional Higgs field, a ${\bf 120}$-dimensional Higgs filed is ntroducedin addition to a ${\bf 10}$-dimensional Higgs field and plays a crucial role to reproduce the realistic charged fermion mass matrices. With contributions of ${\bf 120}$ Higgs field, the original Witten's scenario of inducing the right-handed Majorana neutrino mass through 2-loop diagrams becomes phenomenologically viable. This model inherits the nice features of the conventional renormalizable minimal SO(10) GUT model with…
Motivated by the large mixing angle solutions for the atmospheric and solar neutrino anomalies, flavor changing neutral current processes and lepton flavor violating processes as well as the muon anomalous magnetic moment are analyzed in the framework of SU(5) SUSY GUT with right-handed neutrino. In order to explain realistic mass relations for quarks and leptons, we take into account effects of higher dimensional operators above the GUT scale. It is shown that the supersymmetric (SUSY) contributions to the CP violation parameter in $K^0-\bar{K}^0$ mixing, $ε_K$, the $μ\to e γ$ branching ratio…
General structures of the charged lepton and the neutrino mixing matrices leading to tri-bimaximal leptonic mixing are determined. These are then integrated into an SO(10) model within which detailed fits to fermion masses and mixing angles are given. It is shown that one can obtain excellent fits to all the fermion masses and quark mixing angles keeping tri-bimaximal leptonic mixing intact. Different perturbations to the basic structure are considered and those which can or which cannot account for the recent T2K and MINOS results on the reactor mixing angle $θ_{13}^l$ are identified.
We estimate the CKM matrix elements in the recently proposed minimal model, anti-SU(7) GUT for the family unification, $[\,3\,]+2\,[\,2\,]+8\,[\,\bar{1}\,]$+\,(singlets). It is shown that the real angles of the right-handed unitary matrix diagonalizing the mass matrix can be determined to fit the Particle Data Group data. However, the phase in the right-handed unitary matrix is not constrained very much. We also includes an argument about allocating the Jarlskog phase in the CKM matrix. Phenomenologically, there are three classes of possible parametrizations, $\delq=α,β,$ or $γ$ of the unitari…
The extension of Majorana neutrino mass mechanism of the neutrinoless double-beta decay ($0νββ$) with the inclusion of right-handed leptonic and hadronic currents is revisited. While only the exchange of light neutrinos is assumed, the $s_{1/2}$ and $p_{1/2}$-states of emitted electrons as well as recoil corrections to the nucleon currents are taken into account. Within the standard approximations the decay rate is factorized into a sum of products of kinematical phase-space factors, nuclear matrix elements and the fundamental parameters that characterize the lepton number violation. Unlike in…
A dynamical origin of the Yukawa couplings is a promising scenario to explain the flavour puzzle. The focus of this letter is set on the role of the neutrino Majorana character: when an $O(2)_{N_R}$ flavour symmetry acts on the right-handed neutrino sector, the minimum of the scalar potential allows for large mixing angles -in contrast to the simplest quark case- and predicts a maximal Majorana phase. This leads to a strong correlation between neutrino mass hierarchy and mixing pattern. Realistic solutions point to the existence of three heavy right-handed neutrinos.
Supersymmetric (SUSY) Grand Unified theories (GUTs) generally predict FCNC and CP violating processes to occur both in the leptonic and hadronic sectors. Assuming an underlying SU(5) group plus right-handed neutrinos (RN), we perform an extensive study of FCNC and CP violation, analyzing the correlations between leptonic and hadronic processes like mu-> e gamma and K-Kbar mixing, tau->mu gamma and b -> s transitions such as B_d -> phi K_s and Bs-Bsbar mixing. Moreover, we examine the impact of the considered scenario on the UT analyses, monitoring the low energy consequences implied by possibl…
Assuming the same form of all mass matrices as motivated by quark-lepton symmetry, we discuss conditions under which bi-large mixing in the lepton sector can be obtained with a minimal amount of fine tuning requirements for possible models. We assume hierarchical mass matrices, dominated by the 3-3 element, with off-diagonal elements much smaller than the larger neighboring diagonal element. Characteristic features of this scenario are strong hierarchy in masses of right-handed neutrinos, and comparable contributions of both lighter right-handed neutrinos to the resulting left-handed neutrino …
In the framework of the minimum supersymmetric model with right-handed neutrinos, we consider the Bi-maximal mixing which is realized at the GUT scale and discuss a question that this model can reproduce the low energy phenomena and the leptogenesis.
We study $R$-parity violation in the framework of GUTs, focusing on the case that $R$-parity is broken exclusively through $ΔB=1$, $ΔL=0$ effective interactions. We construct two such models, an $SU(5)$ and an $SU(5)\times U(1)_{X}$ model, in which $R$-parity breaking is induced through interactions with extra supermassive fields. The presence of only the Baryon Number violating operators ${d^c}{d^c}{u^c}$ requires an asymmetry between quarks and leptons, which is achieved either by virtue of the Higgs representations used or by modifications in the matter multiplets. The latter possibility is…
Although $SO(10)$ Supersymmetric (SUSY) Grand Unification Theories (GUTs) are very attractive for neutrino mass and mixing, it is often quite difficult to achieve successful leptogenesis from the lightest right-handed neutrino $N_1$ due to the strong relations between neutrino and up-type quark Yukawa couplings. We show that in a realistic model these constraints are relaxed, making $N_1$ leptogenesis viable. To illustrate this, we calculate the baryon asymmetry of the Universe $ Y_B $ from flavoured $ N_1 $ leptogenesis in a recently proposed $ Δ(27) \times SO(10) $ SUSY GUT. The flavoured Bo…
Precision CP violation measurements in rare hadronic B decays could provide clean signatures of parity symmetric new physics, implying the existence of SU(2)_L x SU(2)_R x U(1)_{B-L} x P symmetry at high energies. New contributions to the weak scale Hamiltonian which respect parity to O(1%) in supersymmetric realizations are compatible with an SU(2)_R breaking scale M_R \le M_GUT, implying that sensitivity to the GUT scale is possible. The generic case of right-handed currents without left-right symmetry is also discussed. A detailed analysis of B -> VV polarization in QCD factorization reveal…
In this paper we propose a low-energy parametrization of the two right-handed neutrino model, and discuss the prospects to determine experimentally these parameters in supersymmetric scenarios. In addition, we present exact formulas to reconstruct the high-energy leptonic superpotential in terms of the low-energy observables. We also discuss limits of the three right-handed neutrino model where this procedure applies.
The correlation between the CP asymmetry in $B\to ϕK_s$ ($S_{ϕK_s}$) and the chromoelectric dipole moment (CEDM) of strange quark ($d_s^C$), which is constrained by the electric dipole moment (EDM) of $^{199}$Hg, is studied in the supersymmetric (SUSY) models with the right-handed squark mixing. It is known that, if the right-handed bottom and strange squarks have a CP-violating mixing, such as in the SUSY SU(5) GUT with right-handed neutrinos, the induced gluon-penguin diagram may give a sizable contribution to $S_{ϕK_s}$. However, when the left-handed bottom and strange squarks also have a m…
We introduce a flavor ${\cal U}(1)$ symmetry à la Froggat-Nielsen to explain the magnitude of the CKM mixing angles as well bilarge mixing in the neutrino sector. In the framework of GUTs we also estimate the magnitude of the third leptonic mixing angle $θ_{13}$. Estimates for rare leptonic decays such as $μ\to e \ga $ are also provided. Finally, leptogenesis is exploited for estimating the magnitude of leptonic CP violation.
We analyze lepton flavor violating $τ\to μγ$ and $μ\to e γ$ processes in SUSY GUT model in which sfermions have special mass spectrum. It is assumed that only third generation sfermions which are contained in ${\bf 10}(Q, U^c, E^c)$ of SU(5) can have a different mass from the others. This mass spectrum is led from $E_6$ GUT model with horizontal symmetries. It is shown that branching ratios of $τ\to μγ$ and $μ\to e γ$ depend strongly on a right-handed stau mass. The weak scale stability requires the light stau, so large decay rates can be expected in this scenario. When stau is around 150 GeV …
Supersymmetric SU(5) GUT augmented with anomaly free U(1)_F flavor symmetry is presented. Very economical field content and U(1)_F charge assignment are obtained by specific construction. In particular, three families of 10+5* chiral matter, along the SU(5) singlet states (some of which serve as right handed neutrinos) are obtained. Appealing texture zero Yukawa matrices provide natural understanding of hierarchies between charged fermion masses and mixings. The model predicts inverted hierarchical neutrino mass scenario with interesting implications.
We study the transference of an initial leptonic charge contained in a complex scalar field (waterfall field) at the end of the inflation to the leptons of the standard model and then convert this leptonic charge in baryonic charge by sphaleron process. The proposal is that this is done trough the decay of the complex scalar field particles into the right-handed neutrino which in turn decays into the left-handed lepton doublet and the Higgs field of the standard model. It must be analyzed in what environment the transference is done. We propose that the inflaton (the dominant energy density of…
The three generation mirror fermion model is compared with LEP precision and low energy data. While for zero mixing of ordinary and mirror fermions the model is not favoured, for non zero mixing very low $χ^2 $ fits have been obtained, in particular when right handed leptonic mixings are small and left handed leptonic mixings are large (of the order of 0.1 radians.)
We study effects of supersymmetric particles in various rare B decay processes as well as in the unitarity triangle analysis. We consider three different supersymmetric models, the minimal supergravity, SU(5) SUSY GUT with right-handed neutrinos, and the minimal supersymmetric standard model with U(2) flavor symmetry. In the SU(5) SUSY GUT with right-handed neutrinos, we consider two cases of the mass matrix of the right-handed neutrinos. We calculate direct and mixing-induced CP asymmetries in the b to s gamma decay and CP asymmetry in B_d to phi K_S as well as the B_s--anti-B_s mixing amplit…
We study the symmetric 2-zero texture of the neutrino mass matrix, which is obtained from the symmetric Dirac neutrino mass matrix with 2-zeros and right-handed Majorana neutrino mass matrix with the general form via the see-saw mechanism, for the SUSY SO(10) GUT model including the Pati-Salam symmetry. We show that the only one texture in our model, having degenerate mass spectrum for the 1st and 2nd generation of right-handed Majorana neutrino, can simultaneously explain the current neutrino experimental data, lepton flavor violating processes and baryon asymmetry of the Universe. Within suc…
We analyze the possibility of universality violation in diagonal leptonic decays of the $Z$ boson, in the context of interfamily "see-saw" models. In a minimal extension of the Standard Model with right-handed neutrino fields, we find that universality-breaking effects increase quadratically with the heavy Majorana neutrino mass and may be observed in the running $LEP$ experiments.
We present a supersymmetric grand unification model based on SO(10) group with $S4$ flavor symmetry. In this model, the fermion masses are from Yukawa couplings involving $\bf{10}$ and $\bar{\bf{126}}$ Higgs multiplets and the flavor structures of mass matrices of both quarks and leptons are determined by spontaneously broken $S4$. This model fits all of the masses and mixing angles of the quarks and leptons. For the most general CP-violation scenario, this model gives $\sinθ_{13}$ a wide range of values from zero to the current bound with the most probable values $0.02-0.09$. With certain ass…
Leptonic flavor-changing $H^0$ decays with branching ratios of the order of $10^{-5}-10^{-6}$ may constitute an interesting framework when looking for large $CP$-violating effects. We show that leptonic $CP$~asymmetries of an intermediate $H^0$ boson can be fairly large in natural scenarios of the minimal Standard Model ($SM$) with right-handed neutrinos, at a level that may be probed at future $H^0$~factories.
We analyse the implications of right-handed neutrinos on the stability of the electroweak vacuum in two-Higgs-doublet models with supersymmetry at high scale. It is assumed that supersymmetry is broken at scale $M_S = 2 \times 10^{16}$ GeV and effective theory below $M_S$ is two-Higgs-doublet model of type II with three generations of singlet neutrinos which induce small masses for the standard model neutrinos through type I seesaw mechanism. We study the high and low scale versions of seesaw mechanism. In both these cases, we show that the presence of right-handed neutrinos significantly impr…
We study CP-conserving non-minimal flavour violation in $A_4 \times SU(5)$ inspired Supersymmetric Grand Unified Theories (GUTs), focussing on the regions of parameter space where dark matter is successfully accommodated due to a light right-handed smuon a few GeV heavier than the lightest neutralino. We find that it is necessary to scan over all NMFV parameters simultaneously in order to properly constrain the space of the model.
We study the baryogenesis via lepton number violation in the model of Anti-GUT. The origin of the baryogenesis is the existence of right-handed Majorana neutrinos which decay in a C, CP and lepton number violation way. The baryon number asymmetry is calculated in the extended Anti-GUT model which is only able to predict order of magnitude-wise. We predicted baryon number to entropy ratio, Y_B=1.46{+5.87\atop-1.17}\times10^{-11}, and this result agrees with experimental values very well.
We perform a renormalisation group analysis of the SO(10) model proposed by Chang, Masiero and Murayama, which links the large atmospheric neutrino mixing angle to loop-induced transitions between right-handed b and s quarks. We compute the impact on B_s-B_s-bar mixing and find that the mass difference in the B_s system can exceed its Standard Model value by a factor of 16.
We analyse the low energy predictions of the minimal supersymmetric standard model (MSSM) arising from a GUT scale Pati-Salam gauge group further constrained by an $A_4 \times Z_5$ family symmetry, resulting in four soft scalar masses at the GUT scale: one left-handed soft mass $m_0$ and three right-handed soft masses $m_1,m_2,m_3$, one for each generation. We demonstrate that this model, which was initially developed to describe the neutrino sector, can explain collider and non-collider measurements such as the dark matter relic density, the Higgs boson mass and, in particular, the anomalous …
Flavor changing neutral current and lepton flavor violating processes are studied in the SU(5) SUSY-GUT with right-handed neutrino supermultiplets. Using input parameters motivated by neutrino oscillation, it is shown that the time-dependent CP asymmetry of $b \to s γ$ can be as large as 20%. We also show that the $B_s$-$\bar{B}_s$ mixing can be significantly different from the standard model prediction.
The present experimental situation regarding neutrino oscillations is first summarized, followed by an overview of selected grand unified models which have been proposed to explain the various scenarios with three active neutrinos and their right-handed counterparts. Special attention is given to the general features of the models and their ability to favor some scenarios over others.
We examine constraints on a model with pure right-handed third generation charged couplings. The parameters of the right-handed mixing matrix and the right-handed coupling strength are constrained from semi-leptonic B decays, the mass difference of neutral mesons, the CP violating observables epsilon and epsilon', and the electric dipole moment of the neutron. We find the model to be tightly constrained by these parameters with several fine tuning conditions on the phases in the right-handed mixing matrix. There is also a necessarily non-zero value of the left and right W mixing parameter. CP …
We point out that the null results of the hadronic electric dipole moment (EDM) searches constrain orbifold grand unified theories (GUTs), where the GUT symmetry and supersymmetry (SUSY) are both broken by boundary conditions in extra dimensions and it leads to rich fermion and sfermion flavor structures. A marginal chromoelectric dipole moment (CEDM) of the up quark is induced by the misalignment between the CP violating left- and right-handed up-type squark mixings, in contrast to the conventional four-dimensional SUSY GUTs. The up quark CEDM constraint is found to be as strong as those from…
An extension of the neutrino sector with two right handed singlet neutrinos responsible for Dirac neutrino masses is discussed. We show that this setup with flavor symmetry can give large solar and atmospheric neutrino mixings and suppressed Theta_13. The flavor symmetry U(1) x S_4 is shown to lead to Theta_23 = π/4 and a new predictive formula for the Theta_13(\simeq 0.015).
In the context of the supersymmetric flipped $SU(5)\otimes U(1)$ GUT model, we have studied in detail the neutrino mass spectrum, obtaining an approximate formula for the corresponding effective three-generation mass matrix. It is found that at least two neutrinos are expected to have extremely small masses of no particular interest. The third neutrino, on the other hand, may eventually get a mass of order $10^{-3}$ eV, of relevance for the solution of the solar neutrino problem with the MSW mechanism, as a consequence of vacuum-expectation-values at the GUT mass scale for some of the scalar p…
The Minimal Lepton Flavour Violation (MLFV) framework is discussed after the recent indication for CP violation in the leptonic sector. Among the three distinct versions of MLFV, the one with degenerate right-handed neutrinos will be disfavoured, if this indication is confirmed. The predictions for leptonic radiative rare decays and muon conversion in nuclei are analysed, identifying strategies to disentangle the different MLFV scenarios. The claim that the present anomalies in the semi-leptonic $B$-meson decays can be explained within the MLFV context is critically re-examined concluding that…
We consider a $U(1)'$ extended supersymmetric model with a right-handed neutrino superfield which can generate light neutrino mass by Type I seesaw mechanism. The lighter superpartner of the right-handed neutrino could be the scalar dark matter. These right-handed sneutrinos can come from the decay of $\tilde{Z'}$, superpartner of the extra gauge boson $Z'$. Left-right handed sneutrino mixings affect their decays further, giving rise to displaced "lepton flavour violating" signatures. A wino-like chargino NLSP (next to lightest supersymmetric particle) creates even more interesting decay topol…
Neutrino masses and mixings are very different from quark masses and mixings. This puzzle is a crucial hint in the search for the mechanism which determines fermion masses in grand unified theories. We study the flavour problem in an SO(10) GUT model in six dimensions compactified on an orbifold. Three sequential families are localized at three branes where SO(10) is broken to its three GUT subgroups. Their mixing with bulk fields leads to large neutrino mixings as well as small mixings among left-handed quarks. The small hierarchy of neutrino masses is due to the mismatch between up-quark and…
A full account is given of the procedure used by the authors to construct an SO(10) supersymmetric grand unified model of the fermion mass matrices. Various features of the model which gives remarkably accurate results for the quark and lepton masses and mixings were presented earlier in separate publications. The construction of the matrices is first discussed in the framework of effective operators, from which one naturally obtains the maximal ν_μ- ν_τmixing, while the small angle or maximal mixing solutions for the solar neutrinos depend upon the nature of the Majorana matrix. A set of Higg…
We investigate low-scale resonant leptogenesis in an $SU(5) \times \mathcal{T}_{13}$ model where a single high energy phase in the complex Tribimaximal seesaw mixing produces the yet-to-be-observed low energy Dirac and Majorana ${CP}$ phases. A fourth right-handed neutrino, required to generate viable light neutrino masses within this scenario, also turns out to be necessary for successful resonant leptogenesis where $CP$ asymmetry is produced by the same high energy phase. We derive a lower bound on the right-handed neutrino mass spectrum in the $\mathrm{GeV}$ range, where part of the paramet…
Lopsided structure in mass matrices of down quarks and leptons gives a simple explanation for the observed large angles of neutrino mixings. We realize such mass matrices by the Froggatt-Nielsen mechanism in the framework of supersymmetric SO(10) grand unified theory (GUT). It is shown that the model can reproduce the successful mass matrices which have been obtained in SU(5) models. Cosmological implication of the model is also discussed. We show that the hybrid inflation occurs naturally in the model and it offers non-thermal leptogenesis by decays of the next-to-lightest right-handed neutri…
We study the μ\to e γdecay in the Z_3-invariant next-to-minimal supersymmetric (SUSY) Standard Model (NMSSM) with superheavy right-handed neutrinos. We assume that the soft SUSY breaking parameters are generated at the GUT scale, not universally as in the minimal supergravity scenario but in such a way that those soft parameters which are specific to the NMSSM can differ from the soft parameters which involve only the MSSM fields while keeping the universality at the GUT scale within the soft parameters for the MSSM and right-handed neutrino fields. We call this type of boundary conditions "se…
