Supersymmetric Left-right Model Research Articles

Neutrino exotica in the skewE6left-right model

With the particle content of the 27 representation of E_6, a skew left-right supersymmetric gauge model was proposed many years ago, with a variety of interesting phenomenological implications. The neutrino sector of this model offers a natural framework for obtaining small Majorana masses for nu_e, nu_mu, and nu_tau, with the added bonus of accommodating 2 light sterile neutrinos.

$\mu-e$ conversion in nuclei in the left-right supersymmetric model

We investigate the contributions to $\mu - e $ conversion in nuclei in a supersymmetric model with left-right symmetry, motivated by the new data on neutrino oscillations. We study the dependence of the conversion rate on the various parameters of the model, and show that light-mass or large $\tan \beta$ scenarios are severely restricted. We analyse the effect of several popular mecahnisms of neutrino mixing on the conversion rate as well as the influence of the right-handed scale on the conversion rate. We compare the conversion rate to the branching ratio for $\mu \rightarrow e \gamma$ and discuss their relative accessibility at future experiments, their sensitivity to various parameters of the model, as well as their relative importance in providing signals for new Physics.

Higgs sector andR-parity breaking couplings in models with brokenU(1)B−Lgauge symmetry

Four different supersymmetric models based on ${\mathrm{SU}(2)}_{L}\ifmmode\times\else\texttimes\fi{}{U(1)}_{R}\ifmmode\times\else\texttimes\fi{}{U(1)}_{B\ensuremath{-}L}$ and ${\mathrm{SU}(2)}_{L}\ifmmode\times\else\texttimes\fi{}{\mathrm{SU}(2)}_{R}\ifmmode\times\else\texttimes\fi{}{U(1)}_{B\ensuremath{-}L}$ gauge symmetry groups are studied. ${U(1)}_{B\ensuremath{-}L}$ symmetry is broken spontaneously by a vacuum expectation value (VEV) of a sneutrino field. The right-handed gauge bosons may obtain their mass solely by a sneutrino VEV. The physical charged lepton and neutrino are mixtures of gauginos, Higgsinos and lepton interaction eigenstates. Explicit formulas for masses and mixings in the physical lepton fields are found. The spontaneous symmetry-breaking mechanism fixes the trilinear R-parity breaking couplings. Only some special R-parity breaking trilinear couplings are allowed. There is a potentially large trilinear lepton number breaking coupling --- which is unique to left-right models --- that is proportional to the ${\mathrm{SU}(2)}_{R}$ gauge coupling ${g}_{R}.$ The couplings are parametrized by few mixing angles, making spontaneous R-parity breaking a natural ``unification framework'' for R-parity breaking couplings in supersymmetric left-right models.

Neutrino magnetic moments in the left-right supersymmetric model

We calculate the magnetic moments of Dirac and Majorana neutrinos in the context of the left-right supersymmetric model. We show that if the theory can generate light Dirac neutrinos, their magnetic dipole moment could be large enough to be experimentally relevant. The transition moments of Majorana neutrinos are smaller than the corresponding ones obtained in the left-right model without supersymmetry and just below the region of interest experimentally.

Signature at the Fermilab Tevatron for the light doubly charged Higgsino of the supersymmetric left-right model

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 between the two highest E_T tau jets when they come from same sign tau leptons can be used to distinguish this model from the others.

The electric dipole moment of the neutron in the left-right supersymmetric model

We calculate the neutron electric dipole moment (EDM) in the left-right supersymmetric model, including one-loop contributions from the chargino, the neutralino and the gluino diagrams. We discuss the dependence of the EDM on the phases of the model, as well as on the mass parameters in the left and right sectors. The neutron EDM imposes different conditions on the supersymmetric spectrum from either the electron EDM, or the neutron EDM in the minimal supersymmetric standard model. The neutron EDM may be a clue to an extended gauge structure in supersymmetry.

Two-intermediate-scale unification analysisof supersymmetric SO(10) at a two-loop level

The process of unification within a supersymmetric left-right (SUSY L-R) model embedded in SO(10) is parametrized in terms of two intermediate scales (one at which L-R symmetry is broken and a second one at which supersymmetry breaks down to the standard model), the numbers of fermion families (F) and scalar multiplets (S), and the value of the strong coupling (0s), which we take to be between 0.110 and 0.130. The analysis is carried out at a two-loop level and analytical expressions for the first-order case are also given. We compare the results of this analysis with those obtained for SUSY SU(5) and L-R SO(10), among which similar analyses have revealed significant differences in the structure of unification within these models. Unlike L-R SO(10), it is found that the Higgs contribution is indispensable to attain unification. It also turns out that a two-intermediate-scale scenario allows more freedom in the actual values of these scales constrained by unification.

Phenomenology of light remnant doubly charged Higgs fields in the supersymmetric left-right model

It has recently been shown that in supersymmetric left-right models with automatic R-parity conservation, the theory below the ${W}_{R}$ scale is given by the MSSM with massive neutrinos and a pair of doubly charged superfields with masses in the 100 GeV range [with or without an extra pair of heavy Higgs doublets $(M>~10 \mathrm{TeV})$ depending on the model]. In this paper we study the unification prospects for such theories and their phenomenological implications for collider experiments. We study two versions of the theory: one with supersymmetry breaking transmitted via the gauge and another where the same occurs via gravitational forces. We point out that looking at multi $\ensuremath{\tau}$ final states can considerably constrain the parameter space of the model.

Constraining the left-right supersymmetric model fromμ→eγandμ→3e

We present a detailed and complete analysis of the lepton-flavor violating decay $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\mu}}e\ensuremath{\gamma}$ to one loop order (terms proportional to ${m}_{\ensuremath{\mu}})$ in the left-right supersymmetric model. We include the mixing of the scalar partners of the left- and right-handed leptons, and show that it leads to a strong enhancement of the branching ratio. We study the distinctive features of the decay in this model and show that it can be distinguished from the same process in the minimal supersymmetric standard model in most scenarios.

Supersymmetry and large scale left-right symmetry

We show that the low energy limit of the minimal supersymmetric Left-Right models is the supersymmetric standard model with an exact R-parity. The theory predicts a number of light Higgs scalars and fermions with masses much below the $B-L$ and $SU(2)_R$ breaking scales. The non-renormalizable version of the theory has a striking prediction of light doubly charged supermultiplets which may be accessible to experiment. Whereas in the renormalizable case the scale of parity breaking is undetermined, in the non-renormalizable one it must be bigger than about $10^{10} - 10^{12}$ GeV. The precise nature of the see-saw mechanism differs in the two versions, and has important implications for neutrino masses.

$\mu\rightarrow e\gamma$ decay in the left-right supersymmetric model

We calculate the rate of the decay $\mu \to e\gamma$ and the electric dipole moment of the electron in the left-right supersymmetric model when the breaking of parity occurs at a considerably large scale. The low-energy flavor violation in the model originates either from the nonvanishing remnants of the left-right symmetry in the slepton mass matrix or from the direct flavor changing lepton-slepton-neutralino interaction. The result is found to be large for the masses of the supersymmetric particles not far from the electroweak scale and already accessible at the current experimental accuracy. It also provides nontrivial constraints of the lepton mixing in the model.

Particle mass limits in minimal and nonminimal supersymmetric models

A review of the Higgs and neutralino sector of supersymmetric models is presented. This includes the upper limit on the mass of the lightest Higgs boson in the minimal supersymmetric standard model, as well as models based on the standard model gauge groupSU(2) L xU(l) Y with extended Higgs sectors. We then discuss the Higgs sector of left-right supersymmetric models, which conserveR-parity as a consequence of gauge invariance, and present a calculable upper bound on the mass of the lightest Higgs boson in these models. We also discuss the neutralino sector of general supersymmetric models based on the SM gauge group. We show that, as a consequence of gauge coupling unification, an upper bound on the mass of the lightest neutralino as a function of the gluino mass can be obtained.

Supersymmetric left-right models and light doubly charged Higgs bosons and Higgsinos

We point out that in a large class of supersymmetric left-right models with automatic $R$-parity conservation there is a pair of light doubly charged Higgs bosons and Higgsinos. Requiring the mass of these particles to satisfy the CERN LEP $Z$-width bound implies that the ${W}_{R}$ mass must be above ${10}^{9}\mathrm{GeV}.$

Mass of the lightest Higgs boson in supersymmetric left-right models

We consider the lightest Higgs boson in naturally R-parity conserving supersymmetric left-right models. We obtain an upper bound on the tree level mass of this lightest Higgs boson. This upper bound depends on the $SU(2)_L$ and $SU(2)_R$ gauge couplings, and the vacuum expectation values of bidoublet Higgs fields, which are needed to break $SU(2)_L\times U(1)_Y$. The upper bound does not depend on either the $SU(2)_R$ breaking scale or the supersymmetry breaking scale. We evaluate the bound numerically by assuming that the theory remains perturbative upto some scale $\Lambda$. We find that the bound can be considerably larger than in MSSM. The dominant radiative corrections to the upper bound due to top-stop and bottom-sbottom systems are of the same form as in the minimal supersymmetric standard model.

Constraining the vacuum expectation values in naturally R-parity conserving supersymmetric models

We obtain a relation between right-handed gauge boson mass and soft squark mass in naturally R-parity conserving general supersymmetric left-right models. This relation implies that either W R is lighter than twice the soft squark mass, or a ratio of vacuum expectation values (VEVs) in the model, denoted by tan α, is close to its value of unity in the limit of vanishing D -terms. Generally, we find that for heavy W R tan α is larger than one, and that the right-handed sneutrino VEV, responsible for spontaneous R -parity breaking, is at most of the order M SUSY h Δ R , where M SUSY is supersymmetry breaking scale and h Δ R is the Yukawa coupling in Majorana mass term for right-handed neutrinos. These constraints follow from SU (3) c and U (1) em gauge invariance of the ground state of the theory.

Explaining the HERA anomaly without giving up R-parity conservation

We point out that in extended supersymmetric models such as supersymmetric left-right models, it is possible to have leptoquarks that explain the HERA high $Q^2$ anomaly without giving up R-parity conservation. The leptoquarks belong to vectorlike $(2, 2, \pm{4/3}, 3 or 3^*) $ representations of $SU(2)_L\times SU(2)_R\times U(1)_{B-L}\times SU(3)_c$ (denoted $G_{2213}$). Unlike the R-parity violating scenario, the leptoquarks are accompanied by new superpartners,the leptoquarkino which leads to many intersting signatures in other collider experiments. At Tevatron, pair productions of the leptoquarkino will give rise to dilepton signals very distinct from the top productions. These models can lead to unification of gauge coupling constants at a scale of around $10^{10}$ GeV implying that grand unification group is not of the usual SU(5) or SO(10) types but rather an automatically R-parity conserving $SU(5)\times SU(5)$ GUT model recently proposed by one of the authors (R. N. M.) which leads to a stable proton.

Doubly charged Higgsino contribution to the decaysμ→eγandμ→3eand to the anomalous magnetic moment of the muonΔaμwithin the left-right supersymmetric model

We present a detailed and complete calculation of the doubly charged Higgsino contribution to the decays mu--> e photon and mu--> 3e and to the anomalous magnetic moment of the muon within the left-right supersymmetric model. We include the mixing of the scalar partners of the left and right handed leptons, and show that it leads to a strong enhancement of the decay modes in certain scenarios. We find that the contribution of the doubly charged Higgsino can be close to the known experimental values and are reachable by future experiments.

FCNCs in left-right symmetric theories and constraints on the right-handed scale

We revise the limits on the FCNC higgses in manifestly left-right symmetric theories. It is shown that the combination of the Kobayashi-Maskawa CP-violation with the tree level $\Delta S=2$ higgs exchange gives very large contribution to the CP-violating $\epsilon$ parameter. It leads to the new strong constraint on the FCNC higgs mass, M>50- 100 TeV, enhanced by factor of the order $\sqrt{m_t/m_c}$. Being addressed to the supersymmetric left-right models, FCNC problem requires both right-handed scale and supersymmetric mass parameters be heavier than 50 TeV for $tan\beta\sim 1$. The most relaxed case corresponds to $tan\beta\sim 20- 30$ where right-handed scale can be of the order of few TeV.

Radiative corrections to theta term in the left-right supersymmetric models

We calculate the radiative correction to the theta term in the generic left-right supersymmetric model due to the Kobayashi-Maskawa source of CP-violation. We found that the value of θ is very sensitive to the relations between vacuum expectation values of bidoublet scalars 〈 φ 1〉 = diag( κ 1, κ′ 1 and 〈 φ 2〉 = diag( κ′ 2, κ 2). The minim value of θ in the model is found to be of order 10 −9 for κ 1 κ 2 ∼ 1 , κ′ 1 = κ′ 2 = 0 in agreement with the experimental constraint without an axion mechanism or fine tuning. In other regions of the parameter space, the radiatively induced θ gives unacceptably large contributions to the electric dipole moment of the neutron.

CP violation in SUSY left-right models

We analyze the minimal supersymmetric left-right model with non-renormalizable interactions induced by higher scale physics and study its CP violating properties. We show that it: (i) solves the strong CP problem; (ii) predicts the neutron electric dipole moment well within experimental limits (thus solving the usual SUSY CP problem). In addition, it automatically conserves R -parity. The key points are that the parity symmetry forces the Yukawa couplings to be hermitean, while supersymmetry ensures that the scalar potential has a minimum with real higgs doublet vacuum expectation values. Gluino and B-L gaugino masses are automatically real. The observed CP violation in the kaon system comes, as in the Standard Model, from the Kobayashi-Maskawa-type phases. These solutions are valid for any value of the right-handed breaking scale M R , as long as the effective theory below M R has only two Higgs doublets that couple fully to fermions. (i.e. the theory below M R is MSSMlike.) The potentially dangerous contributions from the SU (2) L gaugino one-loop diagram as well as from some higher dimensional terms to φ¯ below M R can be avoided if the left-right symmetry originates from a unified theory such as SO(10) and we discuss how this embedding is achieved for the SO(10) case.