We propose an idea that the observed CP violation in neutrino oscillation is originated from the phase in right-handed neutrino mixing by seesaw mechanism. We add small breaking terms $M_{ij}N_{R_i}N_{R_j} $ in model based on $A_4$ symmetry to generate non-diagonal right-handed neutrino mixing, which will give a small correction to TBM mixing via seesaw mechanism with nonzero reactor angle and CP violating phase. We estimate the CP violating phase by investigating the process of leptogenesis due to the decay of right-handed neutrino.
A decay of the gravitino dark matter is an attractive candidate to explain the current excesses of the PAMELA/ATIC cosmic-ray data. However, R-parity violations are required to be very tiny in low-energy scale. We suggest a R-parity violation in the right-handed neutrino sector. The violation is suppressed by a see-saw mechanism. Although a reheating temperature is constrained from above, the thermal leptogenesis is found to work successfully with a help of the R-parity violating right-handed neutrino.
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…
Motivated from the recent results of neutrino oscillation experiment, we investigated lepton flavor violating (LFV) processes in a SU(5) supersymmetric grand unified theory with right-handed neutrino. The current experimental upper bound for $μ\to eγ$ process gives already some constraint on the model. Correlation between $μ\to e γ$ and the SUSY contribution to the muon anomalous magnetic moment is also discussed. Future LFV experiments will give considerable impacts on this type of SUSY GUT models equipped with seesaw neutrino mass generation.
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 formu…
We analyze the lepton number violating (LNV) meson decays that arise in a TeV scale Left Right Symmetry model. The right handed Majorana neutrino $N$ along with the right handed or Standard Model gauge bosons mediate the meson decays and provide a resonant enhancement of the rates if the mass of $N$ ($M_N$) lies in the range $\sim (100\, \rm{MeV}-5\, \rm{GeV})$. Using the expected upper limits on the number of events for the LNV decay modes $M_{1}^{+} \to\ell^{+}\ell^{+}π^{-}$~($M_{1}=B, D, D_{s}, K$), we derive constraints plausible on the mass of the right handed charged gauge boson by futur…
Influence of the neutrino mass submatrix $M_L$ on the e-e- -> W-W- process is discussed. Taking into account various possible CP signatures of heavy neutrinos it is shown that, in some cases, nonzero $M_L$ substantially changes predictions for maximum possible values of the e-e- -> W-W- cross section. A direct role of the $ω^2$ parameter (coming from neutrinoless double beta decay) is clarified. The consequences of doubly charged Higgs particles $δ^{--}$ with resonances even far away from energies of the future linear lepton collider ($\sqrt{s}=0.5-1$ TeV) are studied.
We study the implications of the global U(1)R symmetry present in minimal lepton flavor violating implementations of the seesaw mechanism for neutrino masses. In the context of minimal type I seesaw scenarios with a slightly broken U(1)R, we show that, depending on the R-charge assignments, two classes of generic models can be identified. Models where the right-handed neutrino masses and the lepton number breaking scale are decoupled, and models where the parameters that slightly break the U(1)R induce a suppression in the light neutrino mass matrix. We show that within the first class of mode…
We show that experimental probes of the P-conserving, T-violating triple correlation in polarized neutron or nuclear $β$-decay provide a unique probe of possible T-violation at the TeV scale in the presence of right-handed neutrinos. In contrast to other possible sources of semileptonic T-violation involving only left-handed neutrinos, those involving right-handed neutrinos are relatively unconstrained by present limits on the permanent electric dipole moments of the electron, neutral atoms, and the neutron. On the other hand, LHC results for $pp\to e+$ missing transverse energy imply that an …
Dirac neutrinos with lepton-number-violating interactions can give rise to a new leptogenesis mechanism. In its simplest renormalizable realization, based on a gauged B-L symmetry spontaneously broken by four units, the decay of a new scalar creates an asymmetry in the right-handed neutrinos. A neutrinophilic two-Higgs-doublet model converts this asymmetry to the baryons, provides a natural explanation of the small neutrino masses, and can lead to an effective number of relativistic degrees of freedom of N(eff) = 3.29 due to the entropy-suppressed contribution of the right-handed neutrinos.
In this work we present a new computation of the lepton flavor violating Higgs boson decays that are generated radiatively to one-loop from heavy right-handed neutrinos. We work within the context of the inverse seesaw model with three $ν_R$ and three extra singlets $X$, but the results could be generalized to other low scale seesaw models. The novelty of our computation is that it uses a completely different method by means of the mass insertion approximation which works with the electroweak interaction states instead of the usual 9 physical neutrino mass eigenstates of the inverse seesaw mod…
We investigate the lepton flavor violation in the framework of the MSSM with right-handed neutrinos taking the large mixing angle MSW solution in the quasi-degenerate and the inverse-hierarchical neutrino masses. We predict the branching ratio of $μ\to e+γ$ processes assuming the degenerate right-handed Majorana neutrino masses. We find that the branching ratio in the quasi-degenerate neutrino mass spectrum is 100 times smaller than the ones in the inverse-hierarchical and the hierarchical neutrino spectra. We emphasize that the magnitude of $U_{e3}$ is one of important ingredients to predict …
We study the collider signatures of the left-right twin Higgs model in the case that the right-handed neutrino mass is less than the mass of the right-handed gauge boson. In this scenario, new leptonic decay chains open up, allowing the particles which cancel the one-loop quadratic divergences of the Higgs, the right-handed gauge bosons and top-partners, to be discovered. Half of these events contain same-sign leptons without missing energy, which have no genuine standard model background and for which the backgrounds are purely instrumental. These signals may be used to complement other colli…
The Standard Model extension with additional Lorentz violating terms allows for redefining the equation of motion of a propagating left-handed fermionic particle. The obtained Dirac-type equation can be embedded in a generalized Lorentz-invariance preserving-algebra through the definition of Lorentz algebra-like generators with a light-like preferred axis. The resulting modification to the fermionic equation of motion introduces some novel ingredients to the phenomenological analysis of the cross section of the tritium $β$-decay. Assuming lepton number conservation, our formalism provides a na…
We make a general analysis of neutrino phenomenology for the case neutrino masses are generated by the see-saw mechanism with just two right handed neutrinos. We find general constraints on leptogenesis and lepton flavour violating processes. We also analyse the predictions following from a nontrivial texture zero structure.
The existence of certain TeV suppressed higher-dimension operators may open up new decay channels for the Higgs boson to decay into lighter right-handed neutrinos. These channels may dominate over all other channels if the Higgs boson is light. For a Higgs boson mass larger than $2 m_W$ the new decays are subdominant yet still of interest. The right-handed neutrinos have macroscopic decay lengths and decay mostly into final states containing leptons and quarks. A distinguishing collider signature of this scenario is a pair of displaced vertices violating lepton number. A general operator analy…
During a large period of time, the anomalous baryon number violating interactions are in equilibrium, when the $(B+L)$ asymmetry is washed out. If there is any lepton number violation during this period, that will also erase the $(B-L)$ asymmetry. As a result, survival of the baryon asymmetry of the universe pose strong constraints on lepton number violating interactions. We review here the constraints on the left-handed Majorana neutrino masses arising from this survival requirement of the baryon asymmetry of the universe. We then briefly review models of leptogenesis, where lepton number vio…
Analytic expressions of lepton-flavour- and lepton-number-violating decays of charged leptons are derived in the context of general $SU(2)_L\otimes U(1)_Y$ seesaw scenarios that are motivated by grand unified theories (GUT's) or superstring models, in which left-handed and/or right-handed neutral singlets are present. Possible constraints imposed by cosmology and low-energy data are briefly discussed. The violation of the decoupling theorem in flavour-dependent graphs due to the presence of heavy neutral leptons of Dirac or Majorana nature is emphasized. Numerical estimates reveal that the dec…
Extending the standard model with three right-handed neutrinos ($N_k$) and a second Higgs doublet ($η$), odd under the discrete parity symmetry $Z_2$, Majorana neutrino masses can be generated at 1-loop order. In the resulting model, the lightest stable particle, either a boson or a fermion, might be a dark matter candidate. Here we assume a specific mass spectrum ($M_1\ll M_2 < M_3 < m_η$) and derive its consequences for dark matter and collider phenomenology. We show that (i) the lightest right-handed neutrino is a warm dark matter particle that can give a $\sim$10% contribution to the dark …
We study ``soft leptogenesis'', a new mechanism of leptogenesis which does not require flavour mixing among the right-handed neutrinos. Supersymmetry soft-breaking terms give a small mass splitting between the CP-even and CP-odd right-handed sneutrino states of a single generation and provide a CP-violating phase sufficient to generate a lepton asymmetry. The mechanism is successful if the lepton-violating soft bilinear coupling is unconventionally (but not unnaturally) small. The values of the right-handed neutrino masses predicted by soft leptogenesis can be low enough to evade the cosmologi…
Recently, Nishiura and the author have proposed a unified quark-lepton mass matrix model under a family symmetry U(3)$\times$U(3)$'$. The model can give excellent parameter-fitting to the observed quark and neutrino data. The model has a reasonable basis as far as the quark sector, but the form of the right-handed neutrino mass matrix $M_R$ does not have a theoretical grand, that is, it was nothing but a phenomenological assumption. In this paper, it is pointed out that the form of $M_R$ is originated in structure of neutrino mass matrix for $(ν_i, N_α)$ where $ν_i$ ($i=1,2,3$) and $N_α$ ($α=1…
In minimal left-right symmetric theories, the requirement of parity invariance allows only one complex phase in the Higgs potential and one in the Yukawa couplings, leading to a two-phase theory with both spontaneous and explicit CP violations. We present a systematic way to solve the right-handed quark mixing matrix analytically in this model and find that the leading order solution has the same hierarchical structure as the left-handed CKM matrix with one more CP-violating phase coming from the complex Higgs vev. Armed with this explicit right-handed mixing matrix, we explore its implication…
The lepton number violating interactions generated by the light Majorana neutrinos can erase the primordial baryon asymmetry of the universe during the electroweak phase transition. The Majorana masses of the left-handed neutrinos are constrained to avoid this problem. These constraints do not depend on the $(B-L)$ symmetry breaking mechanism.
We investigate CP violation in the purely right-handed b quark to c- and u- quark coupling model under the constraint of right-handed W-gauge boson mass M_R > 720 GeV , which is experimentally obtained recently by D0 Collaboration at Fermilab. By using the data on $K_L-K_S$ mass difference, CP violating parameter $ε$ in the neutral kaon system and $B_d-\bar B_d$ mixing, together with the new data of $Br (B^-\to ψπ^-) /Br (B^-\to ψK^-) = 0.052 \pm 0.024 (\approx \mid V_{cd}/V_{cs} \mid^2)$, we can fix all of the three independent angles and one phase of the right-handed mixing matrix V^R. Under…
CPT violation in the neutrino sector, suggested as a new way to reconcile different neutrino anomalies, induces at the radiative level observable effects among charged leptons, where high-precision tests of the CPT symmetry are available. We show that, in the models with heavy right-handed Majorana neutrinos, constraints imposed by these experiments require CPT violation in neutrino spectrum be suppressed to a level undetectable for any conceivable neutrino experiment. We find that the CPT violation in the neutrino sector may evade indirect constraints only at the expense of light right-handed…
The lepton flavor violating process μ \rightarrow eγ has been previously studied in a model of electroweak-scale right-handed neutrinos. We have calculated the decay amplitude in unitarity gauge [1] and Rξ gauge [2]. In this paper, we calculate the anomalous magnetic moment of μ in Rξ gauge.
We revisit the neutrino magnetic moments (MMs) in the left-right model with non-manifest symmetry. After deriving an expression in terms of the Dirac and Majorana phases, we analyze the sensitivity of neutrino MMs to these $CP$-violating phases in two scenarios: 1) a maximal right mixing in which left- and right-handed neutrinos are mixed by the same matrix; and 2) a right-handed neutrino mixing whose off-diagonal entries are much smaller than the elements in the diagonal, but where the $CP$ phases remain general. Our results show that, even though certain values of the Majorana phases can eli…
Lepton flavor violating Higgs boson decays are studied within the context of seesaw models with Majorana massive neutrinos. Two models are considered: The SM-seesaw, with the Standard Model Particle content plus three right handed neutrinos, and the MSSM-seesaw, with the Minimal Supersymmetric Standard Model particle content plus three right handed neutrinos and their supersymmetric partners. The widths for these decays are derived from a full one-loop diagrammatic computation in both models, and they are analyzed numerically in terms of the seesaw parameters, namely, the Dirac and Majorana ma…
A simple extension of the Standard Model providing Majorana magnetic moments to right-handed neutrinos is presented. The model contains, in addition to the Standard Model particles and right-handed neutrinos, just a singly charged scalar and a vector-like charged fermion. The phenomenology of the model is analysed and its implications in cosmology, astrophysics and lepton flavour violating processes are extracted. If light enough, the charged particles responsible for the right-handed neutrino magnetic moments could copiously be produced at the LHC.
The LHCb has measured the ratios of $B\to K^\astμ^+μ^-$ to $B\to K^\ast e^+ e^-$ branching fractions in two dilepton invariant mass squared bins, which deviate from the Standard Model predictions by approximately $2.5σ$. These new measurements strengthen the hint of lepton flavor universality breaking which was observed earlier in $B\to K\ell^+\ell^-$ decays. In this work we explore the possibility of explaining these anomalies within the framework of $R$-parity violating interactions. In this framework, $b\to s\ell^+\ell^-$ transitions are generated through tree and one loop diagrams involvin…
We show that the experimental data on $|V_{ub}|$ in various $B$ meson decay modes suggest a possibility of $CP$-violating right-handed current in the $b\to u$ transition. Its consequences in $B\toππ,\,ρρ,\,DK$ are examined and compared with experimental results in order to clarify possible signals of the $CP$ violation in these decay modes. As a result, we find that the $CP$-violating right-handed current is consistent with current experimental data. Its signal might be discovered by precise $CP$ measurements in future experiments.
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.
We investigate the lepton flavor violation in the framework of the MSSM with right-handed neutrinos taking the large mixing angle MSW solution in the quasi-degenerate and the inverse-hierarchical neutrino masses. We predict the branching ratio of $μ\to e+γ$ and $τ\to μ+γ$ processes assuming the degenerate right-handed Majorana neutrino masses. We find that the branching ratio in the quasi-degenerate neutrino mass spectrum is 100 times smaller than the ones in the inverse-hierarchical and the hierarchical neutrino spectra. We emphasize that the magnitude of $U_{e3}$ is one of important ingredie…
We describe supersymmetry breaking by the F-term of a heavy right-handed tau neutrino with a VEV. Due to the the tau neutrino Yukawa coupling, the neutralino, chargino and scalar mass matrices and the weak currents are modified. In addition, there are new cubic and quartic scalar and trilinear R parity violating interactions. For large $\tan β$ these effects may be quite large. The scenario requires low energy supersymmetry breaking with generic values of $F \sim 10^{10}$~GeV.
In this work, we study the charged lepton flavor violating (cLFV) decays $τ-> μγ$, $τ-> 3μ$ and $Z->μτ$ in the framework of the Supersymmetric economical 3-3-1 model. Analytic formulas for branching ratios (BR) of these decays are presented. We assume that there exist lepton flavor violation (LFV) sources in both right- and left-handed slepton sectors. This leads to the strong enhancement of cLFV decay rates. We also show that the effects of the LFV source to the cLFV decay rates in the left-handed slepton sector are greater than those in the right- handed slepton sector. By numerical investig…
The small neutrino mass observed in neutrino oscillations is nicely explained by the seesaw mechanism. Rich phenomenology is generally expected if the heavy neutrinos are not much heavier than the electroweak scale. A model with this feature built in has been suggested recently by Hung. The model keeps the standard gauge group but introduces chirality-flipped partners for the fermions. In particular, a right-handed neutrino forms a weak doublet with a charged heavy lepton, and is thus active. We analyze the lepton flavor structure in gauge interactions. The mixing matrices in charged currents …
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 investigate the effect of B+L - violating anomalous generation of massive right-handed neutrinos on their decoupling, when the right-handed neutrino mass is considerably greater than the right-handed gauge boson masses. Considering normal annihilation channels, the Lee-Weinberg type of calculation, in this case, gives an upper bound of about 700 Gev, which casts doubt on the existence of such a right-handed neutrino mass greater than right-handed gauge boson masses. We examine the possibility that a consideration of anomalous effects related to the SU(2)_R gauge group may turn this into a l…
We investigate charged lepton flavor violating (CFLV) processes in the `neutrinophilic Higgs+seesaw model', in which right-handed neutrinos couple only with an extra Higgs field which develops a tiny VEV and the right-handed neutrinos also have Majorana mass. The model realizes a seesaw mechanism around TeV scale without extremely small Dirac Yukawa couplings. A phenomenological feature of the model is CFLV processes induced by loop diagrams of the charged scalar particles and heavy neutrinos. Therefore, first we constrain the model's parameter space from the search for $μ\to eγ$. Next, we pre…
We discuss a model for neutrino masses and mixings based on R parity violating Yukawa couplings. The model requires no right-handed neutrinos. It accommodates the SuperKamiokande data on atmospheric neutrinos and successfully relates this data to the mass difference for solar neutrinos in the small-angle MSW solution. We obtain an unexpected testable pattern for the three neutrino flavors.
As the hint for CP violating new physics in B-> phi Ks has weakened, we reconsider the possibility of near maximal mixing between \tilde s_R-\tilde b_R squarks. Such a right-handed strange-beauty squark \widetilde{sb}_{1} can be realized by combining supersymmetry with an approximate Abelian flavor symmetry, and comes with a unique new CP violating phase from right-handed quark mixing. Naturally heavy strange-beauty squark and gluino, of order 0.5 to 1 TeV, are easily accommodated by recent time-dependent CP violation measurements in Bd -> phi K^0 and pi^0 K^0. Because of near maximal mixing, …
We review the current status of the leptogenesis scenario originally proposed by Akhmedov, Rubakov and Smirnov (ARS). It takes place in the parametric regime where the right-handed neutrinos are at the electroweak scale or below and the CP-violating effects are induced by the coherent superposition of different right-handed mass eigenstates. Two main theoretical approaches to derive quantum kinetic equations, the Hamiltonian time evolution as well as the Closed-Time-Path technique are presented, and we discuss their relations. For scenarios with two right-handed neutrinos, we chart the viable …
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 study baryogenesis through lepton number violation in left-right symmetric models. In these models the lepton number and CP violating interactions of the triplet higgs scalars can give rise to lepton number asymmetry through non-equilibrium decays of the $SU(2)_L$ triplet higgs and the right handed neutrinos. This in turn generates baryon asymmetry during the electroweak anomalous processes.
We consider supersymmetric (SUSY) models for the muon $g-2$ anomaly without flavor violating masses at the tree-level. The models can avoid LHC constraints and the vacuum stability constraint in the stau-Higgs potential. Although large flavor violating processes are not induced within the framework of minimal SUSY standard model, once we adopt a seesaw model, sizable lepton flavor violating (LFV) processes such as $μ\to e γ$ and $μ\to e$ conversion are induced. These LFV processes will be observed at future experiments such as MEG-II, COMET and Mu2e if right-handed neutrinos are heavier than $…
We present a systematic approach to solve analytically for the right-handed quark mixings in the minimal left-right symmetric model which generally has both explicit and spontaneous CP violations. The leading-order result has the same hierarchical structure as the left-handed CKM mixing, but with additional CP phases originating from a spontaneous CP-violating phase in the Higgs vev. We explore the phenomenology entailed by the new right-handed mixing matrix, particularly the bounds on the mass of $W_R$ and the CP phase of the Higgs vev.
The impact of right-handed currents in both charged- and neutral-current flavour-violating processes is analysed by means of an effective theory approach. More explicitly, we analyse the structure of dimension-six operators assuming a left-right symmetric flavour group, commuting with an underlying $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ global symmetry, broken only by two Yukawa couplings. The model contains a new unitary matrix controlling flavour-mixing in the right-handed sector. We determine the structure of this matrix by charged-current data, where the tension between inclusive and e…
We discuss leptogenesis in a model with heavy right-handed Majorana neutrinos propagating in a constant but otherwise generic CPT-violating axial time-like background (which could be motivated by string theory considerations). At temperatures much higher than the temperature of the electroweak phase transition we solve analytically but approximately (using Pade approximants) the corresponding Boltzmann equations, which describe lepton asymmetry generation due to the tree-level decays of the heavy neutrinos into standard model leptons. These leptons are effectively massless at such temperatures…
We study the seesaw mechanism in the supersymmetric standard model (SSM) with ${\mathbb Z}_3$ symmetry instead of the R-parity, so-called {\it Matter triality} ($M_3$). This Abelian discrete symmetry prohibits the baryon/lepton number violation operators at the non-renormalizable level, and the proton longevity is ensured. The lepton number violation term by the right-handed neutrino is only allowed under the symmetry, it plays a role of the Majorana mass after the right-handed sneutrino develops into the vacuum expectation value. The mass of the active neutrino is generated from the two contr…
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 …
The contribution of the charged right-handed higgsino fields to the chargino mass spectrum in the context of the Left-Right Supersymmetric Model is studied. Analytical expressions for the chargino masses assuming arbitrary CP-violating phases are given. Also, the corresponding inverse parameter problem is studied. Analytical disentangling of some relevant parameters is presented. A general inversion algorithm, based on suitable measurement of cross-section type observables associated to chargino pair production in electron positron annihilation, is proposed.
We discuss the constraints of lepton mixing angles from lepton number violating processes such as neutrinoless double beta decay, (μ^-)-(e^+) conversion and K decay, $K^- \to π^+μ^-μ^-$ which are allowed only if neutrinos are Majorana particles. The rates of these processes are proportional to the averaged neutrino mass defined by $<m_ν >_{a b}\equiv |\sum_{j=1}^{3}U_{a j} U_{b j}m_j|$ in the absence of right-handed weak coupling. Here $a, b (j)$ are flavour(mass) eigen states and $U_{a j}$ is the left-handed lepton mixing matrix. We obtain the consistency conditions which are satisfied irrele…
Assuming the Dirac-type neutrino masses m_D are related to quark or charged lepton masses, neutrino oscillation data indicate that right handed neutrino masses are in general strongly hierarchical. In particular, if m_D is similar to the up-type quark masses, the mass of the lightest right handed neutrino M_1<~10^6 GeV. We show that non-thermal leptogenesis by inflaton decay can yield sufficient baryon asymmetry despite this constraint, and discuss how the asymmetry is correlated with the low energy neutrino masses and CP-violating phases.
We study the one-loop supersymmetric contributions to lepton-flavor violating $Z$ -boson decays in a fully left-right symmetric model. In addition to right-handed scalar neutrinos, the decays could receive important contributions from doubly-charged triplet Higgsinos which couple to leptons only. We find that the decay widths reach present experimental bounds and discuss mass constraints for the contributing supersymmetric partners.
We study lepton flavor violating (LFV) tau and B decays in models with heavy neutrinos to constrain the mixing matrix parameters U_{tau N}. We find that the best current constraints when the heavy neutrinos are purely left-handed come from LFV radiative tau decay modes. To obtain competitive constraints in LFV B decay it is necessary to probe b -> X_{s} tau^{\pm} e^{\mp} at the 10^{-7} level. When the heavy neutrinos have both left and right-handed couplings, the mixing parameters can be constrained by studying LFV B decay modes and LFV tau decay into three charged leptons. We find that the br…
When the standard model is extended with right-handed neutrinos the symmetries of the resulting Lagrangian are enlarged with a new global U(1)R Abelian factor. In the context of minimal seesaw models we analyze the implications of a slightly broken U(1)R symmetry on charged lepton flavor violating decays. We find, depending on the R-charge assignments, models where charged lepton flavor violating rates can be within measurable ranges. In particular, we show that in the resulting models due to the structure of the light neutrino mass matrix muon flavor violating decays are entirely determined b…
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 consider a $U(1)'$ supersymmetric seesaw model in which a right-handed sneutrino is a thermal dark matter candidate whose relic density can be in the right range due to its coupling to relatively light $\tilde{Z'}$, the superpartner of the extra gauge boson $Z'$. Such light $\tilde Z'$ can be produced at the LHC through cascade decays of colored superparticles, in particular, stops and sbottoms, and then decay to a right-handed neutrino and a sneutrino dark matter, which leads to lepton flavor violating signals of same/opposite-sign dileptons (or multileptons) accompanied by large missing e…
Within the domain wall-mediated electroweak baryogenesis, we study fermion scattering off a CP-violating wall in the background of an uniform magnetic field. In particular, we calculate the asymmetry between the reflection coefficients for right-handed and left-handed chiral fermions, ΔR = R_{R \to L} - R_{L \to R}, which is of relevance to non local baryogenesis mechanisms.
