The Minimal Supersymmetric Standard Model with a Bilinear R--Parity Violating Term

Some aspects of bilinear R-Parity violation, the simplest extension of the MSSM which does not conserve R-Parity, are reviewed in comparison with the MSSM. We put special emphasis on the effect of quantum corrections.Comment: 12 pages including 10 figures, Latex. Talk given at the International Workshop on Quantum Effects in the MSSM, 9--13 Sep. 1997, Barcelona, Spai

R--Parity Breaking in Minimal Supergravity

We consider the Minimal Supergravity Model with universality of scalar and gaugino masses plus an extra bilinear term in the superpotential which breaks R-Parity and lepton number. We explicitly check the consistency of this model with the radiative breaking of the electroweak symmetry. A neutrino mass is radiatively induced, and large Higgs-Lepton mixings are compatible with its experimental bound. We also study briefly the lightest Higgs mass. This one-parameter extension of SUGRA-MSSM is the simplest way of introducing R-parity violation.Comment: 5 pages including 2 figures, Latex. Talk given at the International Europhysics Conference on High Energy Physics, EPS-HEP-1997, 19-26 August 1997, Jerusalem. Small change in the acknowledgment

Chargino Production in Different Supergravity Models and the Effect of the Tadpoles

If the lightest chargino is discovered at LEP2, the measurement of its mass and cross section together with the mass of the lightest neutralino, enables the determination of the parameters that define the theory and the entire supersymmetric and Higgs spectrum. Within this context, we: (i) study the effect of the one--loop tadpoles in the minimization condition of the Higgs potential, by comparing the RGE--improved Higgs potential approximation with the calculation of the minimum including the effect of the one--loop tadpoles, and (ii) compare the prediction of two different supergravity models, namely, the model based on $B=2m_0$ and motivated by the solution of the $\mu$--problem, and the minimal supergravity model, based on $A=B+m_0$.Comment: 10 pages, 4 figure

Extracting SUSY Parameters from Selectron and Chargino Production

We review the extraction of fundamental supersymmetric parameters from experimental observables related to the detection of charginos and selectrons at $e^+e^-$ colliders. We consider supergravity models with universal scalar and gaugino masses and radiatively broken electroweak symmetry. Two scenarios are considered: (a) The lightest chargino is light enough to be produced at LEP2, and (b) the right handed selectron is light enough to be produced at LEP2. We show how the validity of supergravity models can be tested even if experimental errors are large. Interesting differences between the spectrum in the two scenarios are pointed out.Comment: 14 pages including 9 figures, Latex. Presented at the Trieste Conference on "Quarks and Leptons: Masses and Mixings", ICTP, 7-11 October 1996, Trieste, Ital

Neutrinos in Supersymmetry

We briefly review the neutrino mass generation mechanism in supersymmetry with Bilinear R-Parity Violation in Minimal Supergravity and Anomaly Mediated Supersymmetry Breaking.Comment: 6 pages, 4 figures. Presented at the 2005 International Linear Collider Workshop LCWS05, Stanford, USA, 18-22 Mar 200

Stop Decays with R-Parity Violation and the Neutrino Mass

The atmospheric and solar neutrino problems can be explained in a supersymmetric scenario where R-parity is broken bilinearly. Within this context we explore the decays of the top squark. We find that the Rp violating decay $\tilde t_1 -> b \tau$ can easily dominate over the Rp conserving decay $\tilde t_1 -> c \tilde\chi^0_1$ and sometimes also over the decay $\tilde t_1 -> b \tilde\chi^+_1$. We study the implications of non-universal boundary conditions at the GUT scale.Comment: 5 pages, 8 figures. Talk given at the International Workshop on Particles in Astrophysics and Cosmology: From Theory to Observation, Valencia, Spain, May 3-8, 199

Bilinear R-Parity Violation

We review some of the main features of Bilinear R-Parity Violation (BRpV), defined by a quadratic term in the superpotential which mixes lepton and Higgs superfields and is proportional to a mass parameter epsilon. We show how large values of epsilon can induce a small neutrino mass without fine-tunning. We mention the effect on the mass of the lightest Higgs boson. Finally we report on the effect of BRpV on gauge and Yukawa unification, showing that bottom-tau unification can be achieved at any value of tan(beta).Comment: 12 pages, including 5 figures, Latex. To appear in the proceedings of the International Workshop "Beyond the Standard Model: From Theory to Experiment", 13-17 October 1997, Valencia, Spai

The Decay b -> s gamma, the Higgs Boson Mass, and Yukawa Unification without R-Parity

We review some properties of Bilinear R-Parity Violating models: simple extensions of the Minimal Supersymmetric Standard Model motivated by spontaneous breaking of R-Parity. We concentrate on the relaxation of the bounds on the charged Higgs mass imposed by the measurement of B(b -> s gamma), the effect on the mass of the lightest neutral Higgs boson, the radiative breaking of the electroweak symmetry, the unification of bottom and tau Yukawa couplings, and the relation of these phenomena to the radiatively generated tau-neutrino mass.Comment: 14 pages, including 7 figures. Based on talk given at the SUSY98 Conference, 11-17 July 1998, Oxford, Englan

Renormalizing Coupled Scalars with a Momentum Dependent Mixing Angle in the MSSM

The renormalization of a system of coupled scalars fields is analyzed. By introducing a momentum dependent mixing angle we diagonalize the inverse propagator matrix at any momentum $p^2$. The zeros of the inverse propagator matrix, \ie, the physical masses, are then calculated keeping the full momentum dependence of the self energies. The relation between this method and others previously published is studied. This idea is applied to the one-loop renormalization of the CP-even neutral Higgs sector of the Minimal Supersymmetric Model, considering top and bottom quarks and squarks in the loops. Presented in the Eighth Meeting of the Division of Particles and Fields of the American Physical Society ``DPF'94'', The University of New Mexico, Albuquerque NM, August 2-6, 1994.Comment: 8 pages, plain tex, 2 figures not included, VAND-TH-94-1

Constraints on Supergravity in the Light Gluino Scenario

Minimal $N=1$ supergravity with a radiatively broken electroweak symmetry group is studied in the light gluino scenario. Constraints from the $b\rightarrow s\gamma$ decay and from the masses of the light CP-even neutral Higgs $m_h$, the lightest chargino $m_{\chi^{\pm}_1}$, and the second lightest neutralino $m_{\chi^0_2}$ are analyzed. We consider models in which the relation $A=B+m_0$ holds. We plot the allowed region in the $\tan\beta-\mu$ plane consistent with chargino/neutralino searches, and an upper bound on $\tan\beta$ given by 1.82 (1.85) for $\mu>0$ ($\mu<0$) is found. We analize the consistency of this upper bound with experimental constraints on the lightest Higgs mass. We find that a gluino with a mass of a few GeV is incompatible with this kind of models.Comment: 14 pages (plain tex), 4 figures not included, VAND-TH-94-11. Presented in the International Symposium ``Physics Doesn't Stop: Recent Developments in Phenomenology'', University of Wisconsin, Madison WI, April 11-13, 199