Search

We carry out a detailed analysis of the scalar sector of the nonminimal supersymmetric standard model with lepton number violation, and study the constraints imposed on it by the stability of the electroweak symmetry breaking vacuum. The model contains a trilinear lepton mumber violating term in the superpotential together with the associated \susy breaking interactions which can give rise to neutrino masses. We evaluate the mass matrices for the various boson and fermion modes and then discuss the effect that the lepton number violating interactions have on the mass spectra using a phenomenological precription to implement the experimental constraints on the light neutrinos mass matrix. We also discuss qualitatively the conditions on the lepton number violating parameters set by the unbounded from below directions, and from the absence of the charge and color breaking minima in this model., Comment: 39 pages, 5 figures, Latex file, ps figures

We carry out a detailed analysis of the nonminimal supersymmetric standard model with lepton number violation. The model contains a unique trilinear lepton number violating term in the superpotential which can give rise to neutrino masses at the tree level. We search for the gauged discrete symmetries realized by cyclic groups which preserve the structure of the associated trilinear superpotential of this model, and which satisfy the constraints of the anomaly cancellation. The implications of this trilinear lepton number violating term in the superpotential and the associated soft supersymmetry breaking term on the phenomenology of the light neutrino masses and mixing is studied in detail. We evaluate the tree and loop level contributions to the neutrino mass matrix in this model. We search for possible suppression mechanism which could explain large hierarchies and maximal mixing angles., Comment: Latex file, 43 pages, 2 figures

Theoretical and phenomenological implications of R-parity violation in supersymmetric theories are discussed in the context of particle physics and cosmology. Fundamental aspects include the relation with continuous and discrete symmetries and the various allowed patterns of R-parity breaking. Recent developments on the generation of neutrino masses and mixings within different scenarios of R-parity violation are discussed. The possible contribution of R-parity-violating Yukawa couplings in processes involving virtual supersymmetric particles and the resulting constraints are reviewed. Finally, direct production of supersymmetric particles and their decays in the presence of R-parity-violating couplings is discussed together with a survey of existing constraints from collider experiments., Comment: 263 pages, latex, updated version submitted to Physics Reports

Based on the R-parity violation option of the minimal supersymmetric Standard Model, we examine the scenario where the massive gravitino, relic from the hot big-bang, is the lightest supersymmetric particle and can decay through one or several of the trilinear R-parity violating interactions. We calculate the rates of the gravitino decay via the various three-body decay channels with final states involving three quarks and/or leptons. By taking into account the present constraints on the trilinear R-parity violating coupling constants and assuming the gravitino and scalar superpartner masses do not exceed ${\cal O}(10TeV)$, it turns out that the gravitinos could easily have decayed before the present epoch but not earlier than the big-bang nucleosynthesis one. Therefore, the considered scenario would upset the standard big-bang nucleosynthesis and we conclude that it does not seem to constitute a natural solution for the cosmological gravitino problem., Comment: 22 pages, Latex file, 5 figures

We consider the single chargino production at Tevatron $p \bar p \to \tilde \nu_i \to \tilde \chi^{\pm}_1 l_i^{\mp}$ as induced by the resonant sneutrino production via a dominant \RPV coupling of type $\l'_{ijk} L_i Q_j D_k^c$. Within a supergravity model, we study the three leptons final state. The comparison with the expected background demonstrate that this signature allows to extend the sensitivity on the \susyq mass spectrum beyond the present LEP limits and to probe the relevant \RPV coupling down to values one order of magnitude smaller than the most stringent low energy indirect bounds. The trilepton signal offers also the opportunity to reconstruct the neutralino mass in a model independent way with good accuracy., Comment: 4 pages

This report summarizes the work of the "R-parity violation group" of the French Research Network (GDR) in Supersymmetry, concerning the physics of supersymmetric models without conservation of R-parity at HERA, LEP, Tevatron and LHC and limits on R-parity violating couplings from various processes. The report includes a discussion of the recent searches at the HERA experiment, prospects for new experiments, a review of the existing limits, and also theoretically motivated alternatives to R-parity and a brief discussion on the implications of R-parity violation on the neutrino masses., Comment: 60 pages, LaTeX, 22 figures, 2 tables

The string one loop renormalization of the gauge coupling constants is examined in abelian orbifold models. The contributions to string threshold corrections independent of the compactification moduli fields are evaluated numerically for several representative examples of orbifold models. We consider cases with standard and non-standard embeddings as well as cases with discrete Wilson lines background fields which match reasonably well with low energy phenomenology. We examine one loop gauge coupling constants unification in a description incorporating the combined effects of moduli dependent and independent threshold corrections, an adjustable Kac-Moody level for the hypercharge group factor and a large mass threshold associated with an anomalous $U(1)$ mechanism., Comment: 24 pages. 2 figures. Revised version: Several misprints corrected. Few minor additions.

We examine for standard-like orbifold compactification models the constraints due to quarks and leptons generation non-universality of soft supersymmetry breaking interactions. We follow the approach initiated by Ibanez and Lust and developed by Brignole, Ibanez and Munoz. The breaking of supersymmetry is represented in terms of dilaton and moduli auxiliary field components and, consistently with a vanishing cosmological constant, is parametrized in terms of the dilaton-moduli mixing angle $\theta $ and the gravitino mass scale $m_g$. The soft breaking interactions (gaugino masses, squarks and sleptons mass matrices, scalars interactions A and B coupling constants) are calculable as a function of these parameters and of the discrete set of modular weight parameters specifying the modular transformation properties of the low-energy fields. We solve the renormalization group one-loop equations for the full set of gauge, Yukawa and supersymmetry breaking coupling constants., Comment: 32 pages