We construct a supersymmeterized version of the model presented by Grimus and Lavoura (GL) in [1] which predicts theta_{23} maximal and theta_{13}=0 in the lepton sector. For this purpose, we extend the flavor group, which is D4 x Z2^{(aux)} in the original model, to D4 x Z5. An additional difference is the absence of right-handed neutrinos. Despite these changes the model is the same as the GL model, since theta_{23} maximal and theta_{13}=0 arise through the same mismatch of D4 subgroups, D2 in the charged lepton and Z2 in the neutrino sector. In our setup D4 is solely broken by gauge singlets, the flavons. We show that their vacuum structure, which leads to the prediction of theta_{13} and theta_{23}, is a natural result of the scalar potential. We find that the neutrino mass matrix only allows for inverted hierarchy, if we assume a certain form of spontaneous CP violation. The quantity |m_{ee}|, measured in neutrinoless double beta decay, is nearly equal to the lightest neutrino mass m3. The Majorana phases phi1 and phi2 are restricted to a certain range for m3 < 0.06 eV. We discuss the next-to-leading order corrections which give rise to shifts in the vacuum expectation values of the flavons. These induce deviations from maximal atmospheric mixing and vanishing theta_{13}. It turns out that these deviations are smaller for theta_{23} than for theta_{13}.
Now the bounds on the lepton-flavor violating (LFV) decay modes of tau lepton are being improved by the Belle experiment in the KEK B factory. In this paper the LFV decay of tau lepton is discussed in the supersymmetric seesaw model, using the current neutrino oscillation data.
We investigate CP violation asymmetry in the decay of tau slepton into a tau neutrino and a chargino in the minimal supersymmetric standard model. The new source of CP violation is the complex mixing in the tau slepton sector. The rate asymmetry between the decays of tau slepton and its CP conjugate process can be of order of $10^{-3}$ in some region of the parameter space of the mSUGRA scenario, which will possibly be detectable in the near-future collider experiments.
Supersymmetric (SUSY) theories include many new parameters, some of which are CP-violating. Assuming that SUSY is found at a future high-energy collider, we examine the decay stop2 -> stop1 tau- tau+ with an eye to obtaining information about the new CP phases. We show that there are two CP-violating asymmetries which can be large in some regions of the SUSY parameter space. These involve measuring one or both of the tau spins. These asymmetries are particularly sensitive to phi_At, the phase of the trilinear coupling A_t.
We analyze the Lepton Flavor Violating (LFV) Higgs decay h -> tau mu in three supersymmetric models: Minimal Supersymmetric Standard Model (MSSM), Supersymmetric Seesaw Model (SSM), and Supersymmetric B-L model with Inverse Seesaw (BLSSM-IS). We show that in generic MSSM, with non-universal slepton masses and/or trilinear couplings, it is not possible to enhance BR(h -> tau mu) without violating the experimental bound on the BR(tau -> mu gamma). In SSM, where flavor mixing is radiatively generated, the LFV process mu -> e gamma strictly constrains the parameter space and the maximum value of B…
It is now a firmly established fact that all family lepton numbers are violated in Nature. In this paper we discuss the implications of this observation for future searches for rare tau decays in the supersymmetric see-saw model. Using the two loop renormalization group evolution of the soft terms and the Yukawa couplings we show that there exists a lower bound on the rate of the rare process mu --> e gamma of the form BR(mu --> e gamma) > C BR(tau --> mu gamma) BR(tau --> e gamma), where C is a constant that depends on supersymmetric parameters. Our only assumption is the absence of cancellat…
We discuss the possible enhancement of the tau lepton events at LHC when the left-handed stau doublet becomes light (which can be even lighter than the right-handed stau). This is illustrated in the constrained supersymmetric seesaw model where the slepton doublet mass is suppressed by the effects of a large neutrino Yukawa coupling. We study a few representative parameter sets in the sneutrino coannihilation regions where the tau sneutrino is NLSP and the stau coannihilation regions where the stau is NLSP both of which yield the thermal neutralino LSP abundance determined by WMAP.
We investigate Lepton-Flavor Violating (LFV) decays of Higgs to muon-tau in the supersymmetric economical 3-3-1 (SUSYE331) model. In the presence of flavor mixing in sleptons {mu,tau} and large values of v/v', the ratio of Br(H -->tau^+mu^-)/Br(H -->tau^+tau^-) can reach to non-negligible values O(10^{-3}), as in many known SUSY models. We predict that for the Standard Model Higgs boson, the LHC may detect its decay to muon and tauon. We also investigate the asymmetry between left and right LFV values of corrections and prove that the LFV effects are dominated by the left FLV term, which is O(…
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…
We present a supersymmetric SU(5) x U(1)_H model, free from gauge anomalies, where the Abelian factor U(1)_H, introduced to account for the hierarchy of fermion masses and mixings, is broken by the same adjoint representations of SU(5) that also break the GUT symmetry. The model predicts approximate, but never exact, bottom-tau Yukawa unification. The deviations are related to group theoretical coefficients and can naturally be at the level of 10%-20%.
The measurement of the trilinear couplings A in the part of the Lagrangian which breaks supersymmetry softly will be a difficult experimental task. In this report the heavy Higgs decays H,A -> stau_1 stau_2 to stau pairs are investigated for measuring the stau trilinear coupling A_tau. Based on detailed simulations of signal and backgrounds for a specific reference point in future high luminosity e+e- linear collider experiments, it is concluded that the parameter $_tau can be determined with a precision at the 10% level in the region of moderate to large tan(beta).
We present two recent developments on lepton flavour violation in the MSSM. 1) The supersymmetric seesaw mechanism can be realized through the exchange of heavy SU(2)_W-triplet states, rather than `right-handed' neutrinos. In this scenario the ratio of the tau --> mu gamma (or tau --> e gamma) and mu --> e gamma rates are unambiguously predicted in terms of the low-energy neutrino parameters. 2) Lepton flavour violating decays of the Higgs bosons, (h, H, A) --> mu tau, are induced at one-loop level. The branching ratios can reach 10^{-4} for large tan(beta) and sizeable smuon-stau mixing. Inte…
We study charged lepton flavour violation in low-scale seesaw models of minimal supergravity, which realize large neutrino Yukawa couplings thanks to approximate lepton-number symmetries. There are two dominant sources of lepton flavour violation in such models. The first source originates from the usual soft supersymmetry-breaking sector, whilst the second one is entirely supersymmetric and comes from the supersymmetric neutrino Yukawa sector. Within the framework of minimal supergravity, we consider both sources of lepton flavour violation, soft and supersymmetric, and calculate a number of …
We compute the lepton flavour violating couplings of Higgs bosons in the Minimal Supersymmetric Standard Model, and show that they can induce the decays (h,H,A) --> mu tau at non-negligible rates, for large tan(beta) and sizeable smuon-stau mixing. We also discuss the prospects for detecting such decays at LHC and other colliders, as well as the correlation with other flavour violating processes, such as tau --> mu gamma and tau --> 3 mu.
We analyze the signal at the Tevatron for the doubly charged Higgs superfield of supersymmetric left-right models with gauge mediated supersymmetry breaking. Due to the presence of a new coupling, the lighter stau is usually less massive than the lightest neutralino and is frequently the NLSP. The fermionic part of the doubly charged Higgs field decays dominantly into two tau leptons plus missing energy (gravitino). We find that the inclusive two tau jets and three tau jets plus missing energy signatures could be observable at Run II of the Tevatron. We also find that the distribution in angle…
We have considered a supersymmetric scenario in which the minimal supersymmetric standard model is augmented with a right-chiral neutrino superfield for each generation. Such a scenario can have a lightest supersymmetric particle (LSP) dominated by the right-chiral sneutrino state and the lighter stau as the next-to-lightest supersymmetric particle (NLSP). This can easily be motivated by assuming a high scale framework of supersymmetry breaking like minimal supergravity (mSUGRA). Due to the extremely small neutrino Yukawa coupling, the decay of the NLSP to the LSP is suppressed and consequentl…
We consider $b$-$τ$ unification in supersymmetric $SU(5)$ grand unified theories (GUTs) with extra matters. The renormalization group runnings of $b$ and $τ$ Yukawa coupling constants may be significantly affected by the existence of extra matters. If the extra matters interact with the standard model particles (and their superpartners) only through gauge interaction, the ratio of the $b$ to $τ$ Yukawa coupling constants at the GUT scale becomes suppressed compared to the case without extra matters. This is mainly due to the change of the renormalization group running of the $SU(3)_C$ gauge co…
Recent observations of neutrino oscillations imply non-zero neutrino masses and flavor violation in the lepton sector, most economically explained by the seesaw mechanism. Within the context of supersymmetry, lepton flavor violation (LFV) among the neutrinos can be communicated by renormalization group flow to the sleptons and from there to the charged leptons. We show that LFV can appear in the couplings of the neutral Higgs bosons, an effect that is strongly enhanced at large tan(beta). In particular, we calculate the branching fraction for tau -> 3 mu and mu -> 3 e mediated by Higgs and fin…
Supersymmetry broken by anomaly mediation suffers from tachyonic slepton masses. A possible solution to this problem results in "decoupling", i.e., the first two generations of sfermions are much heavier than the third one. We note that in this scenario a sizable loop-induced contribution to the neutrino mass matrix results. As an application of this scenario we take advantage of the fact that the decoupling evidently not obeys 2-3 generation exchange symmetry. In the neutrino sector, this 2-3 symmetry (or mu-tau symmetry) is a useful Ansatz to generate zero theta_{13} and maximal theta_{23}. …
Supersymmetry (SUSY) with a long-lived stau is an attractive scenario in the LHC experiments because one can directly observe stau tracks in each SUSY event, and thus precise measurements of SUSY particle masses are possible. In this scenario, we discuss the possibility to observe/measure parity violation in interactions among SUSY particles. Such a measurement will be important in determining spins and chiralities of SUSY particles. We use the last step of the cascade-decay chain: $χ^0\to\tildeττ\to\tildeτ(lν\barν)$, where the polarization of the tau lepton can be determined statistically by …
We present an experimental and theoretical analysis of the ratio of branching ratios R=BR(H^+ -> tau^+ nu)/BR(H^+ -> t b-bar) of charged Higgs boson decays as a discriminant quantity between supersymmetric and non-supersymmetric models.
We consider supersymmetric extension of standard electroweak model with Dirac neutrino masses. In such model for significant region of the parameters right-handed tau sneutrino is the lightest superparticle and right-handed charged tau slepton is the next to lightest superparticle. Due to the smallness of the neutrino masses the right-handed tau slepton is long-lived particle that changes the standard signatures used in the search for supersymmetry at supercolliders. The most striking signatures of such scenario is the existence of highly ionizing tracks and excess of multilepton events that i…
We show that the branching ratio R_{b/tau}=BR(h^0->bb)/BR(h^0->tau tau) of the Higgs boson h^0 may usefully differentiate between the Higgs sectors of the Minimal Supersymmetric Standard Model (MSSM) and non-supersymmetric models such as the Standard Model or its two Higgs doublet extensions. Although at tree level R_{b/tau} is the same in all these models, only in the MSSM can it receive a large radiative correction, for moderate to large values of the parameter tan(beta). Such large corrections are motivated in supersymmetric unified schemes wherein the Yukawa couplings of the b-quark and th…
We discuss the QCD and leading electroweak corrections to the hadronic width of the charged Higgs boson of the MSSM. In our renormalization framework, tan(beta) is defined through Gamma(H^+ -> tau^+ nu_{tau}). We show that a measurement of the hadronic width of H^\pm and/or of the branching ratio of its tau-decay mode with a modest precision of ~20% could be sufficient to unravel the supersymmetric nature of H^\pm in full consistency with the low-energy data from radiative B-meson decays.
We compute the SUSY effective hamiltonian that describes the |ΔS|=1 semileptonic decays of tau leptons. We provide analytical expressions for supersymmetric contribution to tau --> u bar{s} nu_{tau} transition in mass insertion approximation. We show that SUSY contributions may enhance the CP asymmetry of tau --> K pi nu_{tau} decays by several orders of magnitude than the standard model expectations. However, the resulting asymmetry is still well below the current experimental limits obtained by CLEO collaborations. We emphasize that measuring CP rate asymmetry in this decay larger than 10^{-…
Three light sterile neutrinos (ν_e^s, ν_μ^s and ν_τ^s) are introduced to accommodate all the available neutrino data: the atmospheric neutrino anomaly is explained by ν_μ-ν_μ^s oscillation with maximal mixing; the solar one is due to ν_e-ν_e^s oscillation of small angle Mikheyev-Smirnov-Wolfenstein type; the Liquid Scintillation Neutrino Detector data is from ν_e -ν_μoscillations, so that the neutrinos can be the hot component of the dark matter. The big bang nucleosynthesis constraint is satisfied by taking the tau neutrino to be 10 MeV heavy. The ν_τdecay is discussed in a model of gauge med…
Third family Yukawa unification, as suggested by minimal SO(10) unification, is revisited in light of recent experimental measurements and theoretical progress. We characterize unification in a semi-model-independent fashion, and conclude that finite $b$ quark mass corrections from superpartners must be nonzero, but much smaller than naively would be expected. We show that a solution that does not require cancellations of dangerously large tanbeta effects in observables implies that scalar superpartner masses should be substantially heavier than the Z scale, and perhaps inaccessible to all cur…
The existence of large ν_μ-ν_τmixing suggests the likelihood of large smuon-stau mixing in supersymmetric models, leading to μand τnumber violation. In addition to interesting signatures in slepton and neutralino production and decay, this will lead to rare τdecays, such as τ--> mu γ. Recently, it has been pointed out that the τ--> 3μbranching ratio could be substantial in the large \tanβregion of parameter space, due to an induced μ-τ-Higgs vertex. In this paper, another signature, τ--> μηis considered. In the large \tanβregion, it is shown that the branching ratio of τ--> μηis 8.4 times the …
We analyze the lepton flavor violating decays $τ\rightarrow Pl$ ($P=π,η,η';\;l=e,μ$) in the scenario of the minimal R-symmetric supersymmetric standard model. The prediction on the branching ratios BR$(τ\rightarrow P e)$ and BR$(τ\rightarrow P μ)$ is affected by the mass insertion parameters $δ^{13}$ and $δ^{23}$, respectively. These parameters are constrained by the experimental bounds on the branching ratios BR($τ\rightarrow e (μ) γ$) and BR($τ\rightarrow 3e(μ)$). The result shows $Z$ penguin dominates the prediction on BR($τ\rightarrow Pl$) in a large region of the parameter space. The bran…
The Minimal Supersymmetric Standard Model contains in general sources of tau lepton flavour violation which induce the rare decays tau --> mu gamma and tau --> e gamma. We argue in this paper that the observation of both rare processes would imply a lower bound on the radiative muon decay of the form BR(mu --> e gamma) > C BR(tau --> mu gamma) BR(tau --> e gamma). We estimate the size of the constant C without specifying the origin of the tau flavour violation in the supersymmetric model and we discuss the implications of our bound for future searches of rare lepton decays. In particular, we s…
We present a comprehensive update of the bounds on R-Parity violating supersymmetric couplings from lepton-flavour- and lepton-number-violating decay processes. We consider tau and mu decays as well as leptonic and semi-leptonic decays of mesons. We present several new bounds resulting from tau, eta and Kaon decays and correct some results in the literature concerning B-meson decays.
We study the Yukawa unification, in particular, the unification of the Yukawa coupling constants of $b$ and $τ$, in the framework of supersymmetric (SUSY) model. We concentrate on the model in which the SUSY breaking scalar masses are of the order of the gravitino mass while the gaugino masses originate from the effect of anomaly mediation and hence are one-loop suppressed relative to the gravitino mass. We perform an accurate calculation of the Yukawa coupling constants of $b$ and $τ$ at the grand unified theory (GUT) scale, including relevant renormalization group effects and threshold corre…
We analyze the ratio of branching ratios R=BR(H->b b-bar)/BR(H->tau^+ tau^-) of Higgs boson decays as a discriminant quantity between supersymmetric and non-supersymmetric models. This ratio receives large renormalization-scheme independent radiative corrections in supersymmetric models at large \tanβ, which are absent in the Standard Model or Two-Higgs-doublet models. These corrections are insensitive to the supersymmetric mass scale. A detailed analysis in the effective Lagrangian approach shows that, with a measurement of +-21% accuracy, the Large Hadron Collider can discriminate between mo…
A detailed investigation of hybrid inflation and the subsequent reheating process is performed within a mu problem solving supersymmetric model based on a left-right symmetric gauge group. The process of baryogenesis via leptogenesis is especially studied. For mu and tau neutrino masses consistent with the small angle MSW resolution of the solar neutrino problem and the recent results of the SuperKamiokande experiment, we show that maximal mu-tau neutrino mixing can be achieved. The required value of the relevant coupling constant is, however, quite small (of the order 10^{-6}).
In this note we discuss a supersymmetric (SUSY) D4 x Z5 model which leads to vanishing reactor mixing angle theta_13=0 and maximal atmospheric mixing theta_23=pi/4 in the lepton sector at leading order (LO), due to the preservation of non-trivial distinct D4 subgroups in the charged lepton and neutrino sectors, respectively. The solar mixing angle theta_12 remains undetermined and is expected to be of order one. Since right-handed charged leptons transform as singlets under D4, the charged lepton mass hierarchy can be naturally accounted for. The model predicts inverted mass hierarchy for neut…
If the scalar tau $\stau$ is the next lightest supersymmetric particle and decays into a gravitino ($\gravitino$) being the lightest supersymmetric particle, it will have generally a very long lifetime. In this paper, we investigate the possibility to study the decay of such a long lived scalar tau at the LHC. If we can add to the present LHC experiments additional detectors which are able to stop the stau particles and measure the produced decay products, the decay characteristics can be studied precisely at the LHC. We identify a maximum "stopper detector" that could be added in the CMS cave…
We compute the branching ratios for mu-> e gamma, tau-> mu gamma and tau -> e gamma in a supersymmetric model invariant under the flavour symmetry group A4 X Z3 X U(1)_{FN}, in which near tri-bimaximal lepton mixing is naturally predicted. At leading order in the small symmetry breaking parameter u, which is of the same order as the reactor mixing angle theta_{13}, we find that the branching ratios generically scale as u^2. Applying the current bound on the branching ratio of mu -> e gamma shows that small values of u or tan(beta) are preferred in the model for mass parameters m_{SUSY} and m_{…
We investigate the production of the lightest neutral Higgs boson in association with tau sleptons in the CP violating minimal supersymmetric standard model (MSSM) at future high-energy $e^{+}e^{-}$ linear colliders. In parameter space of the constrained MSSM, the production cross section of $e^{+}e^{-}\to h^0\widetildeτ^+_1\widetildeτ^-_1$ can be very substantial at high energies. This process would provide a new production mechanism of neutral Higgs bosons and open a window to probe the Higgs-stau coupling and some soft supersymmetric breaking parameters at next linear colliders.
We investigate the possibility that a minimal realization of left-right supersymmetry can be reachable at a high-energy upgrade of the LHC, expected to operate at a center-of-mass energy of 27 TeV. This minimal scenario has a relatively light $SU(2)_R$ doubly-charged Higgs boson, which could decay dominantly into tau-lepton pairs. We explore the associated signals comprised of at least three hadronically-decaying taus, or with at least two hadronic taus and one same-sign-same-flavor charged lepton pair. Our analysis shows that the former signature is challenging to use for getting handles on t…
The nonsupersymmetric as well as the supersymmetric hybrid inflationary model is reviewed. The scenario of baryogenesis via a primordial leptogenesis is discussed and the role of the nonperturbative electroweak sphaleron effects is analyzed. A supersymmetric model based on a left-right symmetric gauge group, which `naturally' leads to hybrid inflation, is presented. The mu problem is solved, in this model, and the baryon asymmetry of the universe is produced through leptogenesis. For masses of nu_mu, nu_tau from the small angle MSW resolution of the solar neutrino problem and SuperKamiokande, …
From the tau-lepton analysis of the charged Higgs decay of the top quark at the Tevatron, t -> H+ b -> tau+ nu_{tau} b, it is possible to set rather stringent bounds on the (tan(beta),M_{H+})-plane, if one assumes that H+ is a charged member of a generic two-Higgs-doublet model. However, if we consider the possibility that H+ is supersymmetric, then we find that the allowed region in the (tan(beta),M_{H+})-plane can be significantly modified by the MSSM quantum corrections. Throughout our analysis we correlate the top quark results with the limits imposed by radiative and semileptonic B-meson …
Quark and lepton flavor signals are studied in four supersymmetric models, namely the minimal supergravity model, the minimal supersymmetric standard model with right-handed neutrinos, SU(5) supersymmetric grand unified theory with right-handed neutrinos and the minimal supersymmetric standard model with U(2) flavor symmetry. We calculate b --> s(d) transition observables in B_d and B_s decays, taking the constraint from the B_s--B_s-bar mixing recently observed at Tevatron into account. We also calculate lepton flavor violating processes mu --> e gamma, tau --> mu gamma and tau --> e gamma fo…
In the minimal supersymmetric standard model, tau sleptons $\tilde τ_{1,2}$ and neutralinos $\tilde χ^0_{1,2}$ are expected to be among the lightest supersymmetric particles that can be produced copiously at future $e^+e^-$ linear colliders. We analyze $\tilde τ$ pair and $\tilde χ_1^0 \tilde χ_2^0$ production under the assumption $m_{\tilde χ_1^0} < m_{\tilde τ_1} < m_{\tilde χ_2^0}$, allowing the relevant parameters of the SUSY Lagrangian to have complex phases. We show that the transverse and normal components of the polarization vector of the $τ$ lepton produced in $\tilde χ_2^0$ decays of…
Strictly adhering to the standard supersymmetric seesaw mechanism, we present a neutrino mass model which allows successful standard thermal leptogenesis compatible with gravitino cosmology. At least some of the neutrino Yukawa couplings must be much larger than the naive estimates following from the seesaw formula. This leads to large BR(mu->e gamma), detectable in the next round of experiments. Ratios of mu->e gamma, tau->e gamma and tau->mu gamma branching ratios are predicted in terms of the measurable neutrino mass matrix.
We consider the supersymmetric seesaw mechanism induced by the exchange of heavy SU(2)_W triplet states, rather than `right-handed' neutrino singlets, to generate neutrino masses. We show that in this scenario the neutrino flavour structure tested at low-energy in the atmospheric and solar neutrino experiments is directly inherited from the neutrino Yukawa couplings to the triplets. This allows us to predict the ratio of the tau --> mu gamma (or tau --> e gamma) and mu --> e gamma decay rates in terms of the low-energy neutrino parameters. Moreover, once the model is embedded in a grand unifie…
Some models for the lepton sector, based on seesaw extensions of the Standard Model, are discussed in which the mu-tau interchange symmetry is realized in various ways. The symmetries defining such models and their characteristic predictions for lepton mixing are presented.
If the tau neutrino is as heavy as 10 MeV which may have certain astrophysical implications, the neutrino mass pattern is studied so as to accommodate the new oscillation observations. It predicts that the electron neutrino has Marjorana mass around 0.05 eV. A supersymmetric model is described to realize the above scenario.
Model independent tests for symmetry violations in tau decays are important for determining whether the tau lepton is elementary or, instead, macroscopic. Such tests are also significant steps towards resolving the outstanding "e - mu - tau" puzzle. This talk reviews such tests in the context of a general treatment of two-body tau decays which only assumes Lorentz invariance and the tree-like structure of the tau-antitau production-decay sequence. Direct measurement of polarized-partial-widths and of associated ``longitudinal-transverse W-exchange" interference intensities will provide signifi…
We study the Zee-Babu two-loop neutrino mass generation model and look for a possible flavor symmetry behind the tri-bimaximal neutrino mixing. We find that there probably exists the mu-tau symmetry in the case of the normal neutrino mass hierarchy, whereas there may not be in the inverted hierarchy case. We also propose a specific model based on a Froggatt-Nielsen-like $Z_5$ symmetry to naturally accomplish the mu-tau symmetry on the neutrino mass matrix for the normal hierarchy case.
We propose a CP-odd asymmetry in the supersymmetric process e^+e^- \to χ^0_i χ^0_j \to χ^0_j τstau_k by means of the transverse τpolarization. We calculate the asymmetry and cross sections at a future linear collider in the 500 GeV c.m.s. energy range with longitudinal polarized beams and high luminosity. We work in the Minimal Supersymmetric Standard Model with complex parameters μ, M_1 and A_τ. The asymmetry can reach values up to 60 %. We also estimate the sensitivity for measuring the τpolarization necessary to probe the CP asymmetry.
Supersymmetric models with t-b-tau Yukawa coupling unification and unified gaugino masses at the GUT scale with mu >0 show a mild preference for light gluino masses \lesssim 500 GeV. This range of gluino mass is now essentially ruled out by LHC searches. We show that a heavier gluino mass ~ 0.5-3 TeV can also be compatible with excellent t-b-tau Yukawa coupling unification in supersymmetric models with non-universal Higgs masses (NUHM2). The gluino in such models is the lightest colored sparticle, while the squark sector displays an inverted mass hierarchy with m_{\tilde q} ~ 5-20 TeV. We pres…
We examine the possibility that the lepton mixing matrix may exhibit a strong form of mu-tau universality, in which corresponding elements of the mu- and tau-neutrino flavour eigenstates have equal moduli, and find that it is consistent with present data on neutrino oscillations. We point out that in the Dirac case, this is equivalent to symmetry under mu-tau reflection, ie. the combined operation of mu-tau flavour exchange in the MNS matrix with a CP transformation on the whole leptonic sector. We give the most general form for such a mixing matrix, examine the lepton mass matrices under such…
We investigate flavour violating decays of the long-lived lightest slepton and the tau lepton in the coannihilation region of the Minimal Supersymmetric Standard Model with a Seesaw mechanism to generate neutrino masses. We consider a situation where the mass difference between the lightest neutralino, as the Lightest Supersymmetric particle (LSP), and the lightest slepton, as the Next-to-LSP, is smaller than the mass of tau lepton. In this situation, the lifetime of the lightest slepton is very long and it is determined by lepton flavour violating (LFV) couplings because the slepton mainly co…
In the gauge-mediated supersymmetry breaking models with scalar tau as the next-to-lightest supersymmetric particle, a scalar lepton may decay dominantly into its superpartner, tau lepton, and the lightest scalar tau particle. We give detailed formulas for the three-body decay amplitudes and the polarization asymmetry of the outgoing tau lepton . We find that the tau polarizations are sensitive to the model parameters such as the stau mixing angle, the neutralino to slepton mass ratio and the neutralino mixing effect.
