In this work we study the Lepton Flavour Violating semileptonic $τ$ decays: 1) $τ\to μPP$ with $PP= π^+π^-, π^0π^0, K^+K^-, K^0 {\bar K}^0$; 2) $τ\to μP$ with $P=π^0, η, η'$ and 3) $τ\to μV$ with $V = ρ^0, ϕ$. We work within the context of two constrained MSSM scenarios: the CMSSM and NUHM. A full one-(SUSY)loop computation is presented and the importance of the various contributions, the $γ$-, $Z$-, and Higgs bosons mediated ones are analysed. The hadronization of quark bilinears is performed within the chiral framework. Some discrepancies in the predicted rates for BR($τ\to μη$), BR($τ\to μη'$) and BR($τ\to μK^+K^-$) are found with respect to previous estimates, which will be commented here. These three channels will be shown to be the most competitive ones to test simultaneously the Lepton Flavour Violation and the Higgs sector. We further present here a set of approximate formulas for all the semileptonic channels which we believe can be useful for further comparison with present and future data.
Here we review the main results of LFV in the semileptonic tau decays $τ\to μPP$ ($PP = π^+ π^-, π^0 π^0, K^+ K^-, K^0 \bar{K}^0$), $τ\to μP$ ($P = π, η, η^{\prime}$), and $τ\to μV$ ($V = ρ, ϕ$) as well as in $μ-e$ conversion in nuclei within SUSY-seesaw scenarios, and compare our predictions with the present experimental bounds
Lepton flavor violating Higgs boson decays (LFVHD) are studied in the context of the Minimal Supersymmetric Standard Model (MSSM) enlarged with three right handed neutrinos and their supersymmetric partners, and with the neutrino masses being generated by the seesaw mechanism. We compute the partial widths for these decays to one-loop order and analyze numerically the corresponding branching ratios in terms of the MSSM and seesaw parameters. We analyze in parallel the lepton flavor changing $ł_j\to l_i γ$ decays and explore the maximum predicted rates for LFVHD, mainly for $H^0,A^0 \to τ{\bar …
We review the computation of the one-loop radiative corrections from the neutrino/ sneutrino sector to the lightest Higgs boson mass, Mh, within the context of the so-called MSSM-seesaw scenario. This model introduces right handed neutrinos and their supersymmetric partners, the sneutrinos, including Majorana mass terms. We find negative and sizeable corrections to Mh, up to -5 GeV for a large Majorana scale, 10^{13}-10^{15} GeV, and for the lightest neutrino mass in a range 0.1-1 eV. The corrections to Mh are substantially larger than the anticipated ILC precision for large regions of the MSS…
We analyze CP violation in the supersymmetric standard model (MSSM) embedded minimally into a left-right symmetric gauge structure with the seesaw mechanism for neutrino masses. With the plausible assumption of universal scalar masses it is shown that CP violation in the hadron sector of the MSSM is described by a single phase residing in the supersymmetry breaking Lagrangian. This improves the CP properties of the MSSM by providing a natural solution to the SUSY CP problem. Furthermore, $ε'/ε$ vanishes in this model above the seesaw scale; extrapolation to the weak scale then leads to a predi…
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…
We discuss rare meson decays $K^ + \to π^ - \ell ^ + \ell '^ + $ and $D^ + \to K^ - \ell ^ + \ell '^ +$ ($\ell, \ell'=e, μ$) in a supersymmetric extension of the Standard Model with R-parity violation. Estimates of the branching ratios for these decays are presented.
We analyze a minimal bottom-up seesaw scenario where we require the theory to satisfy three phenomenological conditions: (i)it is supersymmetric; (ii) it has a local B-L symmetry as part of the SU(2)_L x SU(2)_R x U(1)_{B-L} gauge theory to implement the seesaw mechanism and (iii) B-L symmetry breaking is such that it leaves R-parity unbroken giving a naturally stable dark matter. We show that in such a theory, one can predict the seesaw scale for neutrino masses to be M_R ~ \sqrt{M_{SUSY} M_{Pl}} ~ 10^{11} GeV. We show that the ground state with this property is a stable minimum and is lower …
We calculate the predictions for lepton flavour violating (LFV) tau and muon decays, $l_j \to l_i γ$, $l_j \to 3 l_i$, $μ-e$ conversion in nuclei and LFV semileptonic tau decays $τ\to μPP$ with $PP= π^+π^-, π^0π^0, K^+K^-, K^0 {\bar K}^0$ $τ\to μP$ with $P=π^0, η, η'$ and $τ\to μV$ with $V = ρ^0, ϕ$, performing the hadronisation of quark bilinears within the chiral framework. We work within a SUSY-seesaw context where the particle content of the Minimal Supersymmetric Standard Model is extended by three right-handed neutrinos plus their corresponding SUSY partners, and where a seesaw mechanism…
In light of recent analyses that have shown that nontrivial hidden-sector dynamics in models of supersymmetry breaking can lead to a significant impact on the predicted low-energy supersymmetric spectrum, we extend these studies to consider hidden-sector effects in extensions of the MSSM to include a seesaw model for neutrino masses. A dynamical hidden sector in an interval of mass scales below the seesaw scale would yield renormalization-group running involving both the anomalous dimension from the hidden sector and the seesaw-extended MSSM renormalization group equations (RGEs). These effect…
Inspired by the recent experimental results which show deviations from the standard model (SM) predictions of $b\rightarrow s \ell^+\ell^-$ transitions, we study the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended by the inverse seesaw mechanism. The trilinear $R$-parity violating terms, together with the chiral mixing of sneutrinos, induce the loop contributions to the $b\rightarrow s \ell^+\ell^-$ anomaly. We study the parameter space of the single-parameter scenario $C^{\rm NP}_{9,μ}=-C^{\rm NP}_{10,μ}=C_{\rm V}$ and the double-parameter scenario $(C_{\rm V},C…
We study the non-leptonic puzzle of $B_{d(s)} \rightarrow K^{(\ast)}\bar{K}^{(\ast)}$ decay in the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended with the inverse seesaw mechanism. In this model, the chiral flip of sneutrinos can contribute to the observables $L_{K\bar{K}}$ and $L_{K^{\ast}\bar{K}^{\ast}}$, that is benefit for explaining the relevant puzzle. We also find that this unique effect can engage in the $B_s$-$\bar{B}_s$ mixing. We utilize the scenario of complex $λ^\prime$ couplings to fulfill the recent stringent constraint of $B_s$-$\bar{B}_s$ mixing…
Superconformal anomalies provide an elegant and economical way to understand the soft breaking parameters in SUSY models; however, implementing them leads to the several undesirable features including: tachyonic sleptons and electroweak symmetry breaking problems in both the MSSM and the NMSSM. Since these two theories also have the additonal problem of massless neutrinos, we have reconsidered the AMSB problems in a class of models that extends the NMSSM to explain small neutrino masses via the seesaw mechanism. In a recent paper, we showed that for a class of minimal left-right extensions, a …
Supersymmetric standard model (MSSM) has two sources of rapid proton decay: (i) R-parity breaking terms and (ii) higher dimensional Planck induced B-violating terms; its extensions to include neutrino masses via the type I seesaw mechanism need not have the first of these problems due to the existence of B-L as a gauge symmetry but for sure always have the second one. If instead, neutrino masses are explained in a type III seesaw extension of the standard model, an anomaly free gauge symmetry different from B-L is known to exist. In this note, it is shown that a realistic supersymmetric versio…
Till today lepton flavor violation has not been observed in processes involving charged leptons. Hence, a search for it is under hot pursuit both in theories and experiments. In our current work, we investigate the rates of rare decay processes such as $τ\rightarrow μγ$ in SU(5) SUSY GUT and found that it satisfies the current bound and is one order below the projected sensitivity. This gives a corroborative argument for the influence of the large top-Yukawa coupling at the GUT scale ($λ_{tG}$) on flavor violating decay rates of leptons which are investigable at low energy electroweak scale $M…
We systematically analyze the radiative corrections to the $S_3$ symmetric neutrino mass matrix at high energy scale, say the GUT scale, in the charged lepton basis. There are significant corrections to the neutrino parameters both in the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM) with large tan$β$, when the renormalization group evolution (RGE) and seesaw threshold effects are taken into consideration. We find that in the SM all three mixing angles and atmospheric mass squared difference are simultaneously obtained in their current 3$σ$ ranges at the electroweak scal…
We examine the renormalization group evolution (RGE) for different mixing scenarios in the presence of seesaw threshold effects from high energy scale (GUT) to the low electroweak (EW) scale in the Standard Model (SM) and Minimal Supersymmetric Standard Model (MSSM). We consider four mixing scenarios namely Tri-Bimaximal Mixing, Bimaximal Mixing, Hexagonal Mixing and Golden Ratio Mixing which come from different flavor symmetries at the GUT scale. We find that the Majorana phases play an important role in the RGE running of these mixing patterns along with the seesaw threshold corrections. We …
The recent experimental results including $R_{K^{(\ast)}}$, $R_{D^{(\ast)}}$, $(g-2)_μ$ and $W$ mass show deviations from the standard model (SM) predictions, implying the clues of new physics (NP). In this work, we investigate the explanations of these anomalies in the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended with the inverse seesaw mechanism. The non-unitarity extent $η_{ee}$ and the loop corrections from the interaction $λ'\hat L \hat Q \hat D$ are utilized to raise the prediction of $W$ mass through muon decays. We also find that the interaction $λ'\ha…
Anomaly mediated supersymmetry breaking (AMSB), when implemented in MSSM is known to suffer from the problem of negative slepton mass squared leading to breakdown of electric charge conservation. We show however that when MSSM is extended to explain small neutrino masses by including a pair of superheavy Higgs triplet superfields (the type II seesaw mechanism), the slepton masses can be deflected from the pure AMSB trajectory and become positive. In a simple model we present in this paper, the seesaw scale is about $10^{13}-10^{14}{\rm GeV}$. Gauge coupling unification can be maintained by emb…
In the context of the supersymmetrized seesaw mechanism embedded in the Minimal Supersymmetric Standard Model (MSSM), complex neutrino Yukawa couplings can induce Electric Dipole Moments (EDMs) for the charged leptons, providing an additional route to seesaw parameters. However, the complex neutrino Yukawa matrix is not the only possible source of CP violation. Even in the framework of Constrained MSSM (CMSSM), there are additional sources, usually attributed to the phases of the trilinear soft supersymmetry breaking couplings and the mu-term, which contribute not only to the electron EDM but …
We show that MSSM with three right handed neutrinos incorporating a renormalizable Type-I seesaw superpotential and no-scale SURGA Kähler potential can lead to a Starobinsky kind of inflation potential along a flat direction associated with gauge invariant combination of Higgs, slepton and right handed sneutrino superfields. The inflation conditions put constraints on the Dirac Yukawa coupling and the Majorana masses required for the neutrino masses and also demands the tuning among the parameters. The scale of inflation is set by the mass of the heaviest right handed neutrino. We also fit the…
We review the main results of the one-loop radiative corrections from the neutrino/sneutrino sector to the lightest Higgs boson mass, M_h, within the context of the so-called MSSM-seesaw scenario where right handed neutrinos and their supersymmetric partners are included in order to explain neutrino masses. For simplicity, we have restricted ourselves to the one generation case. We find sizable corrections to M_h, which are negative in the region where the Majorana scale is large (10^{13} - 10^{15} GeV) and the lightest neutrino mass is within a range inspired by data (0.1 - 1 eV). For some re…
The seesaw-extended MSSM provides a framework in which the observed light neutrino masses and mixing angles can be generated in the context of a natural theory for the TeV-scale. Sneutrino-mixing phenomena provide valuable tools for connecting the physics of neutrinos and supersymmetry. We examine the theoretical structure of the seesaw-extended MSSM, retaining the full complexity of three generations of neutrinos and sneutrinos. In this general framework, new flavor-changing and CP-violating sneutrino processes are allowed, and are parameterized in terms of two $3\times 3$ matrices that respe…
Motivated by the tension between the Higgs mass and muon g-2 in minimal supersymmetric standard model (MSSM), we analyze the muon g-2 in supersymmertic B-L extension of the standard model (BLSSM) with inverse seesaw mechanism. In this model, the Higgs mass receives extra important radiative corrections proportional to large neutrino Yukawa coupling. We point out that muon g-2 also gets significant contribution, due to the constructive interferences of light neutralino effects. The light neutralinos are typically the MSSM Bino like and the supersymmetric partner of U(1)_B-L gauge boson (B'-ino)…
We present a full diagrammatic computation of the one-loop corrections from the neutrino/sneutrino sector to the renormalized neutral CP-even Higgs boson self-energies and the lightest Higgs boson mass, Mh, within the context of the so-called MSSM-seesaw scenario. This consists of the Minimal Supersymmetric Standard Model with the addition of massive right handed Majorana neutrinos and their supersymmetric partners, and where the seesaw mechanism is used for the lightest neutrino mass generation. We explore the dependence on all the parameters involved, with particular emphasis in the role pla…
We study the phenomenology of a supersymmetric left-right model, assuming minimal supergravity boundary conditions. Both left-right and (B-L) symmetries are broken at an energy scale close to, but significantly below the GUT scale. Neutrino data is explained via a seesaw mechanism. We calculate the RGEs for superpotential and soft parameters complete at 2-loop order. At low energies lepton flavour violation (LFV) and small, but potentially measurable mass splittings in the charged scalar lepton sector appear, due to the RGE running. Different from the supersymmetric 'pure seesaw' models, both,…
In this work we study the Lepton Flavour Violating semileptonic tau --> mu f0(980) decay within the context of SUSY-Seesaw Models, where the MSSM spectrum is extended by three right handed neutrinos and their SUSY partners, and where the seesaw mechanism is used to generate the neutrino masses. We estimate its decay rate when it proceeds via the Higgs mediated channel tau --> mu H* --> mu f0(980), where H refers to the CP-even MSSM Higgs bosons h^0 and H^0, and the Lepton Flavour Violating tau mu H vertex is radiatively generated via SUSY loops. In order to describe the f0(980) meson we follow…
We consider the leptonic and semileptonic (SL) lepton flavour violating (LFV) decays of the charged leptons in the minimal supersymmetric standard model (MSSM). The formalism for evaluation of branching fractions for the SL LFV charged-lepton decays with one or two pseudoscalar mesons, or one vector meson in the final state, is given. Previous amplitudes for the SL LFV charged-lepton decays in MSSM are improved, for instance the $γ$-penguin amplitude is corrected to assure the gauge invariance. The decays are studied not only in the model-independent formulation of the theory in the frame of M…
The right--handed neutrino mass matrix that is central to the understanding of small neutrino masses via the seesaw mechanism can arise either (i) from renormalizable operators or (ii) from nonrenormalizable or super-renormalizable operators, depending on the symmetries and the Higgs content of the theory beyond the Standard Model. In this paper, we study lepton flavor violating (LFV) effects in the first class of seesaw models wherein the ν_R Majorana masses arise from renormalizable Yukawa couplings involving a B-L = 2 Higgs field. We present detailed predictions for τ-> μ+ γand μ-> e + γbra…
The Minimal Flavor Violation hypothesis (MFV) is extended to the R-parity violating MSSM, supplemented with a simple seesaw mechanism. The requirement of MFV is shown to suppress lepton and baryon-number violating couplings sufficiently to pass all experimental bounds, in particular those for proton decay, and is thus a viable alternative to R-parity. The phenomenological consequences for FCNC, LFV and colliders are briefly discussed. Typically, MFV predicts sizeable baryon-number violation in some characteristic channels, like single stop resonant production.
We explore phenomenological implications of the minimal supersymmetric standard model (MSSM) with a strong supersymmetry breaking trilinear term. Supersymmetry breaking can trigger electroweak symmetry breaking via a symmetry-breaking seesaw mechanism, which can lead to a low-energy theory with multiple composite Higgs bosons. In this model, the electroweak phase transition can be first-order for some generic values of parameters. Furthermore, there are additional sources of CP violation in the Higgs sector. This opens the possibility of electroweak baryogenesis in the strongly coupled MSSM. T…
We study the renormalization group equations (RGEs) of the neutrino parameters in models of Minimal Lepton Flavor Violation. In such models, the RGEs can be described in terms of flavor spurions, such that only the coefficients depend on the specific model. We explicitly demonstrate this method for the SM and MSSM for both Type-I and Type-III seesaw models. For that purpose, the RGEs of neutrino parameters in the MSSM Type-III seesaw have been computed. We have extended this method to get the evolution equations at second order. The implications for leptogenesis are also discussed.
We revisit a class of $SU(5)$ SUSY GUT models which arise in the context of the spectral cover with Klein Group monodromy $V_4=Z_2\times Z_2$. We show that $Z_2$ matter parities can be realised via new geometric symmetries respected by the spectral cover. We discuss a particular example of this kind, where the low energy effective theory below the GUT scale is just the MSSM with no exotics and standard matter parity, extended by the seesaw mechanism with two right-handed neutrinos.
We present the comaprative study of semileptonic and leptonic decays of D_{s},D^{\pm} and D^0 meson (D\rightarrowM l_{α}^+l_{β}^-,D\rightarrowl_{α}^+l_{β}^-,D\rightarrowl_{α}^+v_{α};α,β=e,μ) within the framework of R-parity violating (R_{p}) Minimal Supersymmetric Standard Model (MSSM). The comparison shows that combination and product couplings (λ_{βiα}λ_{ijq}^{'\ast} or λ_{βqk}'λ_{αjk}^{'\ast}) contribution to the branching fractions of the said processes rocesses(under consideration) is consistent or comparable to the experimental measurements in most of the cases. However, there exists som…
Lepton flavor violation (LFV) has been observed in neutrino oscillations. For charged lepton FV decays only upper limits are known, but sizable branching ratios are expected in many neutrino mass models. High scale models, such as the classical supersymmetric seesaw, usually predict that decays $l_i \to 3 l_j$ are roughly a factor $α$ maller than the corresponding decays $l_i \to l_j γ$. Here we demonstrate that the $Z^0$-penguin diagram can give an enhancement for decays $l_i \to 3 l_j$ in many extensions of the MSSM. We first discuss why the $Z^0$-penguin is not dominant in the MSSM with see…
We investigate the influence of the boundary conditions of minimal supergravity (mSUGRA) on the supersymmetric mechanism for lepton flavour violation (LFV) proposed recently [1], within the framework of the MSSM extended by TeV-scale singlet heavy neutrinos. We find that the consideration of the mSUGRA boundary condition may increase the branching ratios of the muon and tauon decaying into three charged leptons by up to a factor of 5, whereas the corresponding branching ratio for their photonic decays remains almost unchanged.
We update the standard model predictions for the branching ratios of the decays B -> (K,K*,Xs) l^+ l^-, with l=e,mu. Using the measurements of BR(B -> Xs gamma) and BR(B -> K l^+ l^-) as well as the upper limits on BR(B -> (K*,Xs) l^+ l^-)$, we work out model independent bounds on the relevant Wilson coefficients. We show the impact of such bounds on the parameter space of the MSSM with minimal flavour violation and of supersymmetric models with additional sources of flavour changing.
We carefully analyze the renormalization group equations in the type I + II seesaw scenario in the extended standard model (SM) and minimal supersymmetric standard model (MSSM). Furthermore, we present analytic formulae of the mixing angles and phases and discuss the RG effect on the different mixing parameters in the type II seesaw scenario. The renormalization group equations of the angles have a contribution which is proportional to the mass squared difference for a hierarchical spectrum. This is in contrast to the inverse proportionality to the mass squared difference in the effective fiel…
The weak decays of $Λ_b \to Λl^{+} l^{-}$ ($l=e, μ$) are investigated in Minimal Supersymmetric Standard Model (MSSM) and also in Supersymmetric (SUSY) SO(10) Grand Unified Models. In MSSM the special attention is paid to the Neutral Higgs Bosons (NHBs) as they make quite a large contribution in exclusive $B \to X_{s} l^{+} l^{-}$ decays at large $\tanβ$ regions of parameter space of SUSY models, since part of SUSY contributions is proportional to $\tan^{3}β$. The analysis of decay rate, forward-backward asymmetries, lepton polarization asymmetries and the polarization asymmetries of $Λ$ baryo…
Lepton flavor violating Higgs boson decays (LFVHD) are studied in the context of the Minimal Supersymmetric Standard Model (MSSM) being embeded in a mSUGRA scenario that is enlarged with three right handed neutrinos and their supersymmetric partners, and with the neutrino masses being generated by the seesaw mechanism. We compute the partial widths for these decays to one-loop order and analyze numerically the corresponding branching ratios in terms of the mSUGRA and seesaw parameters. We analyze in parallel the lepton flavor changing $ł_j\to l_i γ$ decays and explore the maximum predicted rat…
We study the predictions for BR(mu-> e+gamma) and BR(tau-> e,mu+gamma) in a class of recently proposed horizontal SU(2) model that leads to a 3 X 2 seesaw model for neutrino masses. We consider two such models and obtain the correct bi-large mixing pattern for neutrinos. In these models, the effective low energy theory below the SU(2)_H scale is the MSSM. Assuming a supersymmetry breaking pattern as in the minimal SUGRA models, we find that consistent with present g-2, b->s+gamma and WMAP dark matter constraints on the parameters of the model, the BR(mu-> e+gamma) prediction is accessible to t…
We propose and discuss a new Littlest Seesaw model, realised in the tri-direct CP approach, in which the couplings of the two right-handed neutrinos to the lepton doublets are proportional to $(0,-1,1)$ and $(1,5/2,-1/2)$ respectively with the relative phase $η=-π/2$. This model can give an excellent description of lepton flavour mixing, including an atmospheric neutrino mixing angle in the second octant, in terms of only two input parameters. We show that the observed baryon asymmetry can be generated for the lightest right-handed neutrino mass $M_{1}=1.176\times 10^{11}$ GeV in SM and $M_{1}…
We show that the recent measurements of $B_s-\bar{B}_s$ mass difference, $Δm_s$, by DØ and CDF collaborations give very strong constraints on MSSM scenario with large flavor mixing in the LL and/or RR sector of down-type squark mass squared matrix. In particular, the region with large mixing angle and large mass difference between scalar strange and scalar bottom is ruled out by giving too large $Δm_s$. The allowed region is sensitive to the CP violating phases $δ_{L(R)}$. The $Δm_s$ constraint is most stringent on the scenario with both LL and RR mixing. We also predict the time-dependent CP …
Accurate supersymmetric spectra are required to confront data from direct and indirect searches of supersymmetry. \SUSEFLAV is a numerical tool which is capable of computing supersymmetric spectra accurately for various supersymmetric breaking scenarios applicable even in the presence of flavor violation. The program solves MSSM RGEs with complete $3\times3$ flavor mixing at 2-loop level and one loop finite threshold corrections to all MSSM parameters by incorporating radiative electroweak symmetry breaking conditions. The program also incorporates the Type-I seesaw mechanism with three massiv…
A minimal SO(10) model with {\bf 126} Higgs field breaking B-L symmetry has been shown recently to predict large solar and atmospheric mixings in agreement with observations if it is assumed that the neutrino mass follows from the triplet dominated type II seesaw formula. No additional symmetries need to be assumed for this purpose. We discuss the conditions on the way SO(10) symmetry breaks down to MSSM and the Higgs multiplets in the model, required for the triplet dominated type II seesaw formula to hold. We find that (i) SO(10) must break to a nonminimal SU(5) before breaking to the standa…
We study a new supersymmetric mechanism for lepton flavour violation in muon and tau decays and muon -> e conversion in nuclei, within a minimal extension of the MSSM with low-mass heavy singlet neutrinos and sneutrinos. We find that the decays mu -> e gamma, tau -> e gamma and tau -> mu gamma are forbidden in the supersymmetric limit of the theory, whereas other processes, such as mu -> eee, mu -> e conversion, tau -> eee and tau -> e mu mu, are allowed and can be dramatically enhanced several orders of magnitude above the observable level by potentially large neutrino Yukawa coupling effects…
The discovery of a relatively heavy Standard Model (SM) -like Higgs boson challenges naturalness of the minimal supersymmetric standard model (MSSM) from both Higgs and dark matter (DM) sectors. We study these two aspects in the MSSM extended by the low-scale inverse seesaw mechanism. Firstly, it admits a sizable radiative correction on the Higgs boson mass m_h, up to \sim 4 GeV in the case of an IR-fixed point of the coupling Y_νLH_uν^c and a large sneutrino mixing. Secondly, the lightest sneutrino, highly complex as expected, is a viable thermal DM candidate. Owing to the correct relic densi…
We study the effects of heavy Majorana neutrinos on the Higgs sector of the MSSM via radiative corrections. We work within the SUSY context where the MSSM particle content is enlarged with right handed neutrinos and their corresponding SUSY partners, the sneutrinos, and where compatibility with neutrino data is required. We compute the one-loop corrections to the mass of the lightest MSSM CP-even neutral Higgs boson from Majorana neutrinos and their SUSY partners and assume a seesaw mechanism of type I for neutrino mass generation. A negative and sizeable Higgs mass correction of up to -5 GeV …
The existence of an anomalous U(1) symmetry is shown to play a crucial role in the supersymmetric radiative seesaw model for neutrino masses. It explains the smallness of some couplings related to neutrino mass generation in a favorable way in addition to cause the hierarchical structure of Yukawa couplings of quarks and leptons. If it is spontaneously broken to a $Z_2$ subgroup, this $Z_2$ symmetry can make a lifetime of the lightest field with its odd parity extremely long. Thus, the model has an additional dark matter candidate other than the lightest neutralino, which appears in the $R$-pa…
We present a model where neutrino masses are generated by a combination of spontaneous R-parity violation and Type III seesaw. In addition to the usual MSSM particle content, our model consists of one extra triplet matter chiral superfield containing heavy SU(2) triplet fermions and its superpartners. R-parity is broken spontaneously when the sneutrinos associated with the one heavy neutrino as well as the three light neutrinos get vacuum expectation values, giving rise to the mixed $8\times 8$ neutralino-neutrino mass matrix. We show that our model can comfortably explain all the existing neu…
An anomaly free non-universal $U(1)_{X}$ extension to the Minimal Supersymmetric Standard Model is proposed, where additional two $SU(2)$ doublet superfields and four singlet superfields complement the scalar sector of the model. The fermion sector is extended by considering additional superfields containing three quark singlets, two charged lepton singlet superfields and six neutral leptons. A tree-level massless electron is found so radiative corrections are considered to match the mass spectrum with both SUSY and non-SUSY contributions. Likewise, a massless neutrino is found and analytic ex…
We describe recent extensions of the program SPheno including flavour aspects, CP-phases, R-parity violation and low energy observables. In case of flavour mixing all masses of supersymmetric particles are calculated including the complete flavour structure and all possible CP-phases at the 1-loop level. We give details on implemented seesaw models, low energy observables and the corresponding extension of the SUSY Les Houches Accord. Moreover, we comment on the possiblities to include MSSM extensions in SPheno.
In this paper we review our main results for Lepton Flavour Violating (LFV) semileptonic tau decays and muon-electron conversion in nuclei within the context of two Constrained SUSY-Seesaw Models, the CMSSM and the NUHM. The relevant spectrum is that of the Minimal Supersymmetric Standard Model extended by three right handed neutrinos, $ν_{R_i}$ and their corresponding SUSY partners, ${\tilde ν}_{R_i}$, ($i=1,2,3$). We use the seesaw mechanism for neutrino mass generation and choose a parameterisation of this mechanism that allows us to incorporate the neutrino data in our analysis of LFV proc…
We study flavour violation in a supersymmetric SO(10) implementation of the type II seesaw mechanism, which provides a predictive realization of triplet leptogenesis. The experimental upper bounds on lepton flavour violating processes have a significant impact on the leptogenesis dynamics, in particular they exclude the strong washout regime. Requiring successful leptogenesis then constrains the otherwise largely unknown overall size of flavour-violating observables, thus yielding testable predictions. In particular, the branching ratio for mu -> e gamma lies within the reach of the MEG experi…
We propose a new class of R-parity violating extension of MSSM with type II seesaw mechanism for neutrino masses where an unstable gravitino is the dark matter of the Universe. It decays predominantly into three leptons final states, thereby providing a natural explanation of the positron excess but no antiproton excess in the PAMELA experiment. The model can explain neutrino masses without invoking any high scale physics while keeping the pre-existing baryon asymmetry of the universe in tact.
We revisit the standard argument to estimate the scale of new physics (NP) beyond the SM, based on the sensitivity of the Higgs mass to quadratic divergences. Although this argument is arguably naive, the corresponding estimate, Lambda_SM < 2-3 TeV, works reasonably well in most cases and should be considered a conservative bound, as it ignores other contributions to the Higgs mass which are potentially large. Besides, the possibility of an accidental Veltman-like cancellation does not raise significantly Lambda_SM. One can obtain more precise implications from fine-tuning arguments in specifi…
We study a supersymmetric version of the seesaw mechanism type-III. The model consists of the MSSM particle content plus three copies of 24 superfields. The fermionic part of the SU(2) triplet contained in the 24 is responsible for the type-III seesaw, which is used to explain the observed neutrino masses and mixings. Complete copies of 24 are introduced to maintain gauge coupling unification. These additional states change the beta functions of the gauge couplings above the seesaw scale. Using mSUGRA boundary conditions we calculate the resulting supersymmetric mass spectra at the electro-wea…
We systematically investigate constraints on the parameters of the supersymmetric type-I seesaw mechanism from the requirement of successful thermal leptogenesis in the presence of upper bounds on the reheat temperature $T_\mathrm{RH}$ of the early Universe. To this end, we solve the flavour-dependent Boltzmann equations in the MSSM, extended to include reheating. With conservative bounds on $T_\mathrm{RH}$, leading to mildly constrained scenarios for thermal leptogenesis, compatibility with observation can be obtained for extensive new regions of the parameter space, due to flavour-dependent …
