44 research outputs found
Solar Neutrino Rates, Spectrum, and its Moments : an MSW Analysis in the Light of Super-Kamiokande Results
We re-examine MSW solutions of the solar neutrino problem in a two flavor
scenario taking (a) the results on total rates and the electron energy spectrum
from the 1117-day SuperKamiokande (SK) data and (b) those on total rates from
the Chlorine and Gallium experiments. We find that the SMA solution gives the
best fit to the total rates data from the different experiments. One new
feature of our analysis is the use of the moments of the SK electron spectrum
in a analysis. The best-fit to the moments is broadly in agreement
with that obtained from a direct fit to the spectrum data and prefers a comparable to the SMA fit to the rates but the required mixing angle is
larger. In the combined rate and spectrum analysis, apart from varying the
normalization of the B flux as a free parameter and determining its
best-fit value we also obtain the best-fit parameters when correlations between
the rates and the spectrum data are included and the normalization of the B
flux held fixed at its SSM value. We observe that the correlations between the
rates and spectrum data are important and the goodness of fit worsens when
these are included. In either case, the best-fit lies in the LMA region.Comment: 17 pages, 4 figure
Three Generation Neutrino Oscillation Parameters after SNO
We examine the solar neutrino problem in the context of the realistic three
neutrino mixing scenario including the SNO charged current (CC) rate. The two
independent mass squared differences and are taken to be in the solar and atmospheric ranges
respectively. We incorporate the constraints on m as obtained
by the SuperKamiokande atmospheric neutrino data and determine the allowed
values of , and from a combined
analysis of solar and CHOOZ data. Our aim is to probe the changes in the values
of the mass and mixing parameters with the inclusion of the SNO data as well as
the changes in the two-generation parameter region obtained from the solar
neutrino analysis with the inclusion of the third generation. We find that the
inclusion of the SNO CC rate in the combined solar + CHOOZ analysis puts a more
restrictive bound on . Since the allowed values of
are constrained to very small values by the CHOOZ experiment there is no
qualitative change over the two generation allowed regions in the plane. The best-fit comes in the LMA region and
no allowed area is obtained in the SMA region at 3 level from combined
solar and CHOOZ analysis.Comment: One reference added. Version to apprear in PR
Energy Independent Solution to the Solar Neutrino Anomaly including the SNO data
The global data on solar neutrino rates and spectrum, including the SNO
charged current rate, can be explained by LMA, LOW or the energy independent
solution -- corresponding to near-maximal mixing. All the three favour a mild
upward renormalisation of the Cl rate. A mild downward shift of the
neutrino flux is favoured by the energy independent and to a lesser extent the
LOW solution, but not by LMA. Comparison with the ratio of SK elastic and SNO
charged current scattering rates favours the LMA over the other two solutions,
but by no more than .Comment: 18 pages, latex, 3 figure
Anomalous Cosmic Rays and their Ionization States
Ionization states of 16 individual anomalous cosmic ray events have been determined in the anuradha cosmic ray experiment conducted onboard Spacelab-3. The geomagnetic field was used as a rigidity filter for the energetic charged particles, and the upper limit on their ionization states is obtained by using the relation Z <= M.p.c/R/sub c/. Out of 16 events, 11 are found to be singly ionized and the other five events are consistent with their being in singly ionized states. The singly ionized nature of the anomalous cosmic ray particles suggests neutrals in the local interstellar space as their source
Power law enhancement of neutrino mixing angles in extra dimensions
We study the renormalization of the -type Majorana neutrino mass
operator in a scenario where there is a compactified extra dimension and the
fields involved correspond to only the standard model particles and their
Kaluza-Klein excitations. We observe that in a two flavour scenario, where one
of the neutrinos is necessarily , it is indeed possible to generate a
large mixing at 100 GeV starting from a very small mixing near the
ultra-violet cutoff 30 TeV. {\em En passant}, we also derive the Higgs
mass upper and lower limits from perturbative unitarity and stability of the
potential, respectively.Comment: Latex, 6 pages, one pslatex figure; v2: clarifying remarks added,
minor typos corrected, references updated, version to appear in Phys. Rev.
Relation between CPT Violation in Neutrino masses and mixings
The neutrino parameters determined from the solar neutrino data and the
anti-neutrino parameters determined from KamLAND reactor experiment are in good
agreement with each other. However, the best fit points of the two sets differ
from each other by about eV in mass-square differenc and by about
in the mixing angle. Future solar neutrino and reactor anti-neutrino
experiments are likely to reduce the uncertainties in these measurements. This,
in turn, can lead to a signal for CPT violation in terms a non-zero difference
between neutrino and anti-neutrino parameters. In this paper, we propose a CPT
violating mass matrix which can give rise to the above differences in both
mass-squared difference and mixing angle and study the constraints imposed by
the data on the parameters of the mass matrix.Comment: 10page
Neutrinoless double-beta decay with three or four neutrino mixing
Considering the scheme with mixing of three neutrinos and a mass hierarchy
that can accommodate the results of solar and atmospheric neutrino experiments,
it is shown that the results of solar neutrino experiments imply a lower bound
for the effective Majorana mass in neutrinoless double-beta decay, under the
natural assumptions that massive neutrinos are Majorana particles and there are
no unlikely fine-tuned cancellations among the contributions of the different
neutrino masses. Considering the four-neutrino schemes that can accommodate
also the results of the LSND experiment, it is shown that only one of them is
compatible with the results of neutrinoless double-beta decay experiments and
with the measurement of the abundances of primordial elements produced in
Big-Bang Nucleosynthesis. It is shown that in this scheme, under the
assumptions that massive neutrinos are Majorana particles and there are no
cancellations among the contributions of the different neutrino masses, the
results of the LSND experiment imply a lower bound for the effective Majorana
mass in neutrinoless double-beta decay.Comment: 18 pages including 2 figures, RevTe
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
Neutrino oscillation constraints on neutrinoless double beta decay
We have studied the constraints imposed by the results of neutrino
oscillation experiments on the effective Majorana mass || that characterizes
the contribution of Majorana neutrino masses to the matrix element of
neutrinoless double-beta decay. We have shown that in a general scheme with
three Majorana neutrinos and a hierarchy of neutrino masses (which can be
explained by the see-saw mechanism), the results of neutrino oscillation
experiments imply rather strong constraints on the parameter ||. From the
results of the first reactor long-baseline experiment CHOOZ and the Bugey
experiment it follows that || < 3x10^{-2} eV if the largest mass-squared
difference is smaller than 2 eV^2. Hence, we conclude that the observation of
neutrinoless double-beta decay with a probability that corresponds to || >
10^{-1} eV would be a signal for a non-hierarchical neutrino mass spectrum
and/or non-standard mechanisms of lepton number violation.Comment: 20 pages, including 4 figure
Can lepton flavor violating interactions explain the LSND results?
If the atmospheric and the solar neutrino problem are both explained by
neutrino oscillations, and if there are only three light neutrinos, then all
mass-squared differences between the neutrinos are known. In such a case,
existing terrestrial neutrino oscillation experiments cannot be significantly
affected by neutrino oscillations, but, in principle there could be an anomaly
in the neutrino flux due to new neutrino interactions. We discuss how a
non-standard muon decay would modify the
neutrino production processes of these experiments. Since violation
is small for New Physics above the weak scale one can use related
flavor-violating charged lepton processes to constrain these decays in a model
independent way. We show that the upper bounds on ,
muonium-antimuonium conversion and rule out any observable
effect for the present experiments due to
for , respectively. Applying similar arguments to
flavor-changing semi-leptonic reactions we exclude the possibility that the
"oscillation signals" observed at LSND are due to flavor-changing interactions
that conserve total lepton number.Comment: 21 pages, 6 figures, Latex; minor correction