53 research outputs found
Axino-Neutrino Mixing in Gauge-Mediated Supersymmetry Breaking Models
When the strong CP problem is solved by spontaneous breaking of an anomalous
global symmetry in theories with gauge-mediated supersymmetry breaking, the
pseudo Goldstone fermion (the axino) is a good candidate of a light sterile
neutrino. Its mixing with neutrinos relevant for current neutrino experiments
can arise in the presence of R-parity violation. The realistic four neutrino
mass matrix is obtained when the see-saw mechanism is brought in, and an ansatz
for the right-handed neutrino mass is constructed.Comment: Revtex, 7 pp. Version to appear in Phys. Lett.
Unknowns after the SNO Charged-Current Measurement
We perform a model-independent analysis of solar neutrino flux rates
including the recent charged-current measurement at the Sudbury Neutrino
Observatory (SNO). We derive a universal sum rule involving SNO and
SuperKamiokande rates, and show that the SNO neutral-current measurement can
not fix the fraction of solar oscillating to sterile neutrinos. The
large uncertainty in the SSM B flux impedes a determination of the sterile
neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC
measuremen
Anomalous diffusion modifies solar neutrino fluxes
Density and temperature conditions in the solar core suggest that the
microscopic diffusion of electrons and ions could be nonstandard:
Diffusion and friction coefficients are energy dependent, collisions are not
two-body processes and retain memory beyond the single scattering event.
A direct consequence of nonstandard diffusion is that the equilibrium energy
distribution of particles departs from the Maxwellian one (tails goes to zero
more slowly or faster than exponentially) modifying the reaction rates.
This effect is qualitatively different from temperature and/or composition
modification: Small changes in the number of particles in the distribution
tails can strongly modify the rates without affecting bulk properties, such as
the sound speed or hydrostatic equilibrium, which depend on the mean values
from the distribution.
This mechanism can considerably increase the range of predictions for the
neutrino fluxes allowed by the current experimental values (cross sections and
solar properties) and can be used to reduce the discrepancy between these
predictions and the solar neutrino experiments.Comment: 16 pages, ReVTeX, no figures. Text partially revised (24 april 1998
Proton-antiproton annihilation into massive leptons
We extend previous calculations of polarization observables for the
annihilation reaction to the case of heavy
leptons, such as the -lepton. We consider the case when the beam and/or
the target are polarized, as well as the polarization of the outgoing leptons.
We give the dependence of the unpolarized cross section, angular asymmetry, and
various polarization observables on the relevant kinematical variables in the
center of mass and in the laboratory system, with particular attention to the
effect of the mass induced terms.Comment: 25 pages, 8 figure
Do experiments suggest a hierarchy problem?
The hierarchy problem of the scalar sector of the standard model is
reformulated, emphasizing the role of experimental facts that may suggest the
existence of a new physics large mass scale, for instance indications of the
instability of the matter, or indications in favor of massive neutrinos. In the
see-saw model for the neutrino masses a hierarchy problem arises if the mass of
the right-handed neutrinos is larger than approximatively GeV: this
problem, and its possible solutions, are discussed.Comment: revtex, 4 pages, 1 figur
Charged lepton Flavor Violation in Supersymmetry with Bilinear R-Parity Violation
The simplest unified extension of the Minimal Supersymmetric Standard Model
with bi-linear R-parity violation naturally predicts a hierarchical neutrino
mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We
study whether the individual violation of the lepton numbers L_{e,mu,tau} in
the charged sector can lead to measurable rates for BR(mu->e gamma)and
$BR(tau-> mu gamma). We find that some of the R-parity violating terms that are
compatible with the observed atmospheric neutrino oscillations could lead to
rates for mu->e gamma measurable in projected experiments. However, the Delta
m^2_{12} obtained for those parameters is too high to be compatible with the
solar neutrino data, excluding therefore the possibility of having measurable
rates for mu->e gamma in the model.Comment: 29 pages, 8 figures. Constraint from solar neutrino data included,
conclusions changed respect v
Flavor Alignment in SUSY GUTs
A Supersymmetric Grand unified model is constructed based on SO(10)xSO(10)
symmetry in which new types of Yukawa matrices couple standard and exotic
fermions. Evolution of these couplings from the Grand Unified scale to the
electroweak scale causes some of them to be driven to their fixed points. This
solves the supersymmetric alignment problem and ensures that there are no
observable flavor changing neutral currents mediated by supersymmetric
particles. Fermion hierarchy and neutrino mixing constraints are automatically
satisfied in this formalism.Comment: 20 pages, 1 figur
See-saw mechanism and four light neutrino state
A formal proof is given that in a see-saw type neutrino mass matrix with only
two neutrino mass scales () and the maximal rank of , we
can not get a fourth light sterile neutrino.Comment: 5 page
Lepton-flavor violating decays as probes of quantum gravity?
Lepton flavor violating decays and are considered. It is shown that these decays can reach sizeable
magnitudes if some specific lepton-flavor violating 4-fermion operators are
generated by low scale quantum gravity effects, or by some other new physics at
a TeV scale.Comment: 18 pages, 1 figures, LaTeX, uses FEYNMAN package. New references
adde
Can R-parity violation explain the LSND data as well?
The recent Super-Kamiokande data now admit only one type of mass hierarchy in
a framework with three active and one sterile neutrinos. We show that neutrino
masses and mixings generated by R-parity-violating couplings, with values
within their experimental upper limits, are capable of reproducing this
hierarchy, explaining all neutrino data particularly after including the LSND
results.Comment: 7 pages, Latex, 3 PS figures; in v2 a few clarifying remarks included
and two references added (to appear in Physical Review D
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