22 research outputs found
Herbicide Resistant Ryegrass in Oklahoma and Ryegrass Control Options for Spring 2009
Plant and Soil Science
Supernova Bounds on Supersymmetric -parity Violating Interactions
We re-examine resonant massless-neutrino conversions in a dense medium
induced by flavour changing neutral current (FCNC) interactions. We show how
the observed energy spectra from SN1987a and the supernova
-process nucleosynthesis provide constraints on supersymmetric models with
parity violation, which are much more stringent than those obtained from
the laboratory. We also suggest that resonant massless-neutrino conversions may
play a positive role in supernova shock reheating. Finally, we examine the
constraints on explicit -parity-violating FCNCs in the presence of non-zero
neutrino masses in the eV range, as indicated by present hot dark matter
observations.Comment: latex file, 19 pages, including 5 figure
R-parity Conserving Supersymmetry, Neutrino Mass and Neutrinoless Double Beta Decay
We consider contributions of R-parity conserving softly broken supersymmetry
(SUSY) to neutrinoless double beta (\znbb) decay via the (B-L)-violating
sneutrino mass term. The latter is a generic ingredient of any weak-scale SUSY
model with a Majorana neutrino mass. The new R-parity conserving SUSY
contributions to \znbb are realized at the level of box diagrams. We derive
the effective Lagrangian describing the SUSY-box mechanism of \znbb-decay and
the corresponding nuclear matrix elements. The 1-loop sneutrino contribution to
the Majorana neutrino mass is also derived.
Given the data on the \znbb-decay half-life of Ge and the neutrino
mass we obtain constraints on the (B-L)-violating sneutrino mass. These
constraints leave room for accelerator searches for certain manifestations of
the 2nd and 3rd generation (B-L)-violating sneutrino mass term, but are most
probably too tight for first generation (B-L)-violating sneutrino masses to be
searched for directly.Comment: LATEX, 29 pages + 4 (uuencoded) figures appende
Supersymmetry and neutrinoless double beta decay
Neutrinoless double beta decay (0 nu beta beta) induced by superparticle exchange is investigated. Such a supersymmetric (SUSY) mechanism of 0 nu beta beta decay arises within SUSY theories with R-parity nonconservation (R(p)). We consider the minimal supersymmetric standard model (MSSM) with explicit R(p) terms in the superpotential (R(p) MSSM). The decay rate for the SUSY mechanism of 0 nu beta beta decay is calculated. Numerical values for nuclear matrix elements for the experimentally most interesting isotopes are calculated within the proton-neutron quasiparticle random phase approximation. Constraints on the R(p) MSSM parameter space are extracted from current experimental half-life limits. The most stringent limits are derived from data on Ge-76. It is shown that these constraints are more stringent than those from other low-energy processes and are competitive with or even more stringent than constraints expected from accelerator searches
Signatures of spontaneously broken r parity and solar neutrino oscillations
Matter-enhanced neutrino-oscillation parameters can be probed in a variety of conventional experiments in supergravity models where the small neutrino mass arises from spontaneous R-parity violation. A combined analysis of astrophysical and laboratory limits tends to exclude regions of oscillation parameters where the high-energy neutrinos are adiabatically converted. This suggests the possibility of a large reduction in the pp and Be7 neutrino flux even for a mildly reduced B8 neutrino flux, thus stressing the importance of gallium experiments
Supersymmetric majoron signatures and solar neutrino oscillations
Spontaneous R-parity breaking in supergravity solves the solar neutrino problem through matter-enhanced neutrino oscillations. The model may be tested in collider experiments and through ''dynamical'' effects associated with the existence of a weakly interacting majoron. Apart from astrophysical effects, majoron emission can produce observable changes in μ and τ decay spectra for parameter values that substantially reduce the solar neutrino flux. A signature of the model is the possible observation of the decay μ→e+majoron