227 research outputs found
Three dimensional calculation of flux of low energy atmospheric neutrinos
Results of three-dimensional Monte Carlo calculation of low energy flux of atmospheric neutrinos are presented and compared with earlier one-dimensional calculations 1,2 valid at higher neutrino energies. These low energy neutrinos are the atmospheric background in searching for neutrinos from astrophysical sources. Primary cosmic rays produce the neutrino flux peaking at near E sub=40 MeV and neutrino intensity peaking near E sub v=100 MeV. Because such neutrinos typically deviate by 20 approximately 30 from the primary cosmic ray direction, three-dimensional effects are important for the search of atmospheric neutrinos. Nevertheless, the background of these atmospheric neutrinos is negligible for the detection of solar and supernova neutrinos
Do Solar Neutrino Experiments Imply New Physics?
None of the 1000 solar models in a full Monte Carlo simulation is consistent
with the results of the chlorine or the Kamiokande experiments. Even if the
solar models are forced artifically to have a \b8 neutrino flux in agreeement
with the Kamiokande experiment, none of the fudged models agrees with the
chlorine observations. The GALLEX and SAGE experiments, which currently have
large statistical uncertainties, differ from the predictions of the standard
solar model by and , respectively.Comment: 7 pages (figures not included), Institute for Advanced Study number
AST 92/51. For a hard copy with the figures, write: [email protected]
Neutrino Masses within the Minimal Supersymmetric Standard Model
We investigate the possibility of accommodating neutrino masses compatible
with the MSW study of the Solar neutrino deficit within the minimal
supersymmetric Standard Model. The ``gravity-induced'' seesaw mechanism based
on an interplay of nonrenormalizable and renormalizable terms in the
superpotential allows neutrino masses , with the
corresponding quark mass and GeV, while at the same
time ensuring the grand desert with the gauge coupling unification at
GeV. The proposed scenario may be realized in a
class of string vacua, {\it i.e.,} large radius ()
Calabi-Yau spaces. In this case
and . Here GeV is the scale of the tree level (genus zero) gauge coupling ()
unification.Comment: 14 pg. (The value of the tree level gauge coupling unification scale
in string theory has been revised. In addition, the authors would like to
appologize to the readers for erroneously submitting the paper to the HEPTH
bulletin board instead of the HEPPH one.
Quintessence Cosmology and the Cosmic Coincidence
Within present constraints on the observed smooth energy and its equation of
state parameter, it is important to find out whether the smooth energy is
static (cosmological constant) or dynamic (quintessence). The most dynamical
quintessence fields observationally allowed are now still fast-rolling and no
longer satisfy the tracker approximation if the equation of state parameter
varies moderately with cosmic scale. We are optimistic about distinguishing
between a cosmological constant and appreciably dynamic quintessence, by
measuring average values for the effective equation of state parameter.
However, reconstructing the quintessence potential from observations of any
scale dependence appears problematic in the near future. For our flat universe,
at present dominated by smooth energy in the form of either a cosmological
constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed
mass fraction to be maximal at the observed smooth energy/matter ratio.
Identifying this collapsed fraction as a conditional probability for habitable
galaxies, we infer that the prior distribution is flat. Interpreting this prior
as a distribution over theories, rather than as a distribution over
unobservable subuniverses, leads us to heuristic predictions about the class of
future quantum cosmology theories and the static or quasi-static nature of the
smooth energy.Comment: Typos corrected, as presented at Cosmo-01 Workshop, Rovaniemi,
Finland and accepted for publication in Physical Review D. 9 pages, 4 figure
The Earth Effect in the MSW Analysis of the Solar Neutrino Experiments
We consider the Earth effect in the MSW analysis of the Homestake,
Kamiokande, GALLEX, and SAGE solar neutrino experiments. Using the
time-averaged data and assuming two-flavor oscillations, the large-angle region
of the combined fit extends to much smaller angles (to ) than when the Earth effect is ignored. However, the additional constraint
from the Kamiokande II day-night data excludes most of the parameter space
sensitive to the Earth effect independent of astrophysical uncertainties, and
leaves only a small large-angle region close to maximal mixing at 90\% C.L. The
nonadiabatic solution remains unaffected by the Earth effect and is still
preferred. Both theoretical and experimental uncertainties are included in the
analysis.Comment: (11 pages, Revtex 3.0 (can be changed to Latex), 3 postscript figures
included, UPR-0570T
Gamma Rays and the Decay of Neutrinos from SN1987A
We calculate limits to the properties of massive, unstable neutrinos using
data from gamma-ray detectors on the Pioneer Venus Orbiter Satellite; a massive
neutrino emitted from SN1987A that decayed in flight and produced gamma rays
would be detectable by this instruments. The lack of such a signal allows us to
constrain the branching ratio to photons (\Bg), mass (\mnu), and radiative
lifetime (\tau_\gamma = \tau/\Bg). For low mass (m) neutrinos
decaying , \Bg<3\times 10^{-7}, for \mt\lesssim
10^6 \keV\sec, and \Bg<6\times 10^{-14} \mt/\keV\sec for \mt\gtrsim 10^6
\keV\sec; limits for high-mass neutrinos are somewhat weaker due to Boltzmann
suppression. We also calculate limits for decays that produce gamma rays
through the \brem channel, . In the case that
neutrino mass states are nearly degenerate, , our limits
for the mode become more stringent by a factor of
, because more of the decay photons are shifted into the PVO
detector energy window.Comment: 17 pages, 6 postscript figures, uses revtex, epsf.sty. Submitted to
PRD. Also available at
file://ftp.cita.utoronto.ca/cita/jaffe/papers/pvoflux.ps.g
Comment on ``Neutrino masses and mixing angles in a predictive theory of fermion masses''
In the extension of the Dimopoulos--Hall--Raby model of the fermion mass
matrices to the neutrino sector, there is an entry in the up-quark and neutrino
Dirac mass matrices which can be assumed to arise from the Yukawa coupling of a
{\bf 120}, instead of a {\bf 10} or a {\bf 126}, of SO(10). Although this
assumption leads to an extra undetermined complex parameter in the model, the
resulting lepton mixing matrix exhibits the remarkable feature that the does not mix with the other two neutrinos. Making a reasonable
assumption about the extra parameter, we are able to fit the large-mixing-angle
MSW solution of the solar-neutrino problem, and we obtain eV, the right mass range to close the Universe. Other possibilities for
explaining the solar-neutrino deficit are also discussed.Comment: standard LATEX, 6 pages, 2 figures available from the authors, report
No. CMU-HEP93-20 and DOE-ER/40682-4
See-saw Enhancement of Lepton Mixing
The see-saw mechanism of neutrino mass generation may enhance lepton mixing
up to maximal even if the Dirac mass matrices of leptons have structure similar
to that in the quark sector. Two sets of conditions for such an enhancement are
found. The first one includes the see-saw generation of heavy Majorana masses
for right-handed neutrinos and a universality of
Yukawa couplings which can follow from the unification of neutrinos with new
superheavy neutral leptons. The second set is related to lepton number symmetry
of the Yukawa interactions in the Dirac basis of neutrinos. Models which
realize these conditions have strong hierarchy or strong degeneration of
Majorana masses of the right-handed neutrinos.Comment: 16 pages, plain TeX document, Institute for Advanced Study number AST
93/1
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