475 research outputs found
Bounds on Dark Matter from the ``Atmospheric Neutrino Anomaly''
Bounds are derived on the cross section, flux and energy density of new
particles that may be responsible for the atmospheric neutrino anomaly. Decay of primordial
homogeneous dark matter can be excluded.Comment: 10 pages, TeX (revtex
Testing maximal electron and muon neutrino oscillations with sub-GeV SuperKamiokande atmospheric neutrino data
Motivated by the Exact Parity Model and other theories, the hypothesis that
each of the known neutrinos oscillates maximally with a sterile partner has
been put forward as an explanation of the atmospheric and solar neutrino
anomalies. We provide detailed predictions for muon and electron flux ratios
induced in the Kamiokande and SuperKamiokande detectors by sub-GeV atmospheric
neutrinos. Several different, carefully chosen cuts on momentum and zenith
angle are proposed, emphasizing the role of up-down flux asymmetries.Comment: LaTeX, 8 figures, 17 pages, version to appear in Phys. Rev. D Rapid
Communication
Measuring Atmospheric Neutrino Oscillations with Neutrino Telescopes
Neutrino telescopes with large detection volumes can demonstrate that the
current indications of neutrino oscillation are correct or if a better
description can be achieved with non-standard alternatives. Observations of
contained muons produced by atmospheric neutrinos can better constrain the
allowed region for oscillations or determine the relevant parameters of
non-standard models. We analyze the possibility of neutrino telescopes
measuring atmospheric neutrino oscillations. We suggest adjustments to improve
this potential. An addition of four densely-instrumented strings to the AMANDA
II detector makes observations feasible. Such a configuration is competitive
with current and proposed experiments.Comment: 36 pages, 21 figures, revte
Two-Loop Neutrino Masses and the Solar Neutrino Problem
The addition of singlet right-handed neutrinos to the Standard Model
leads to radiatively generated mass corrections for the doublet
neutrinos. For those neutrinos which are massless at the tree level after this
addition, this implies a small mass generated at the two-loop level via
exchange. We calculate these mass corrections exactly by obtaining an
analytic form for the general case of doublets and singlets. As a
phenomenological application, we consider the case and examine the masses
and mixings of the doublet neutrinos which arise as a result of the two-loop
correction in the light of experimental data from two sources which may shed
light on the question of neutrino masses. These are(a) the neutrino detectors
reporting a solar neutrino deficit (and its resolution via
Mikheyev-Smirnov-Wolfenstein matter oscillations), and
(b) the COBE satellite data on the non-zero angular variations of the cosmic
microwave background temperature (and its possible implications for hot dark
matter). Within the framework of the extension considered here, which leaves
the gauge group structure of the Standard Model intact, we show that it is
possible for neutrinos to acquire small masses naturally, with values which are
compatible with current theoretical bias and experimental data.Comment: 24 pages, Two figures, attached as postscript files at the end,
Latex, CTP-TAMU-76/93, MRI-PHY-12/93, LTH-32
Common Origin for the Solar and Atmospheric Neutrino Deficits
Some typos corrected, slightly different abstract, same plots, results and
conclusions.Comment: 14 Latex pages, 3 figures attached as postscript files, IFP-472-UNC,
PRL-TH-93/1
Possible Revelation of Seesaw Mass Pattern in Solar and Atmospheric Neutrino Data
Assuming the solar and atmospheric neutrino deficits to be due to neutrino
oscillations, it is shown that the 3X3 mass matrix spanning the e, mu, and tau
neutrinos may have already revealed a seesaw mass pattern. Also, this matrix is
the natural reduction of a simple 5X5 seesaw mass matrix with one large scale,
the 4X4 reduction of which predicts that a fourth neutrino would mix with the e
and mu neutrinos in such a way that oscillations between them may occur just
within the detection capability of the LSND (Liquid Scintillator Neutrino
Detector) experiment.Comment: 10 pages (4 figures not included
Constraints on Three-Neutrino Mixing from Atmospheric and Reactor Data
Observations of atmospheric neutrinos are usually analyzed using the
simplifying approximation that either or
two-flavor mixing is relevant. Here we
instead consider the data using the simplifying approximation that only one
neutrino mass scale is relevant. This approximation is the minimal three-flavor
notation that includes the two relevant two-flavor approximations. The
constraints in the parameter space orthogonal to the usual, two-flavor analyses
are studied.Comment: 15 pages, preprint IUHET-26
On the Atmospheric Neutrino Anomaly and its Statistical Significance
An analysis of the existing data on the atmospheric neutrino anomaly is
presented, focused on the statistical significance that can be attributed to
its experimental evidence. Our approach is alternative to the usual analyses in
terms of the ratio of event rates. In fact, we perform a comparison
between data and expectations, by {\em separating\/} the information on
-like and -like events, with a careful estimate of the different errors
and of their correlation effects. The results are shown both numerically and
graphically, and disclose interesting aspects of the atmospheric neutrino
anomaly, that the use of the ratio would partially hide, both in the
sub-GeV and in the multi-GeV energy range.Comment: Revised version, Uuencoded, compressed postscript file (16 pages plus
4 figures), to appear in Phys. Rev. D. Notice that the abstract is also
revise
Three-flavor atmospheric neutrino anomaly
We investigate the indications of flavor oscillations that come from the
anomalous flavor composition of the atmospheric neutrino flux observed in some
underground experiments. We study the information coming from the
neutrino-induced -like and -like events both in the sub-GeV energy
range (Kamiokande, IMB, Fr{\'e}jus, and NUSEX experiments) and in the multi-GeV
energy range (Kamiokande experiment). First we analyze all the data in the
limits of pure and
oscillations. We obtain that
oscillations provide a better fit, in particular
to the multi-GeV data. Then we perform a three-flavor analysis in the
hypothesis of dominance of one neutrino square mass difference, , implying
that the neutrino mixing is parametrized by two angles,
. We explore the space
exhaustively, and find the regions favored by the oscillation hypothesis. The
results are displayed in a form suited to the comparison with other flavor
oscillation searches at accelerator, reactor, and solar experiments. In
the analysis, we pay particular attention to the earth matter effects, to the
correlation of the uncertainties, and to the symmetry properties of the
oscillation probability.Comment: 25 pages (RevTeX) + 12 figures, requires epsfig.sty. All the figures
are bitmapped. Postscript figures with full resolution are available at
ftp://ftp.sns.ias.edu/pub/lisi/atmpaper
- âŠ