29 research outputs found
Solar Neutrino Oscillation Parameters after KamLAND
We explore the impact of the data from the KamLAND experiment in constraining
neutrino mass and mixing angles involved in solar neutrino oscillations. In
particular we discuss the precision with which we can determine the the mass
squared difference and the mixing angle
from combined solar and KamLAND data. We show that the precision with which
\Delta m^_{solar} can be determined improves drastically with the KamLAND
data but the sensitivity of KamLAND to the mixing angle is not as good. We
study the effect of enhanced statistics in KamLAND as well as reduced
systematics in improving the precision. We also show the effect of the SNO salt
data in improving the precision. Finally we discuss how a dedicated reactor
experiment with a baseline of 70 km can improve the
sensitivity by a large amount.Comment: Talk given at 4th International Conference on Nonaccelerator New
Physics (NANP 03), Dubna, Russia, 23-28 Jun 200
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
Exploring the sensitivity of current and future experiments to
However the allowed range of () did not change
much with the inclusion of the KamLAND results. In this paper we probe if
future data from KamLAND can increase the accuracy of the allowed range in
and conclude that even after 3 kton-year of statistics and
most optimistic error estimates, KamLAND {\it may} find it hard to
significantly improve the bounds on the mixing angle obtained from the solar
neutrino data. We discuss the sensitivity of the survival
probabilities in matter (vacuum) as is relevant for the solar (KamLAND)
experiments. We find that the presence of matter effects in the survival
probabilities for neutrinos give the solar neutrino experiments SK and
SNO an edge over KamLAND, as far as sensitivity is concerned,
particularly near maximal mixing. Among solar neutrino experiments we identify
SNO as the most promising candidate for constraining and make a
projected sensitivity test for the mixing angle by reducing the error in the
neutral current measurement at SNO. Finally we argue that the most accurate
bounds on can be achieved in a reactor experiment, if the
corresponding baseline and energy can be tuned to a minimum in the survival
probability. We propose a new reactor experiment which can give the value of
to within 14%. We also discuss the future Borexino and
LowNu experiments.Comment: Treatment of KamLAND systematics includes the most optimistic
estimates. Final conclusion unchanged. Version to appear in PR
Testing the solar LMA region with KamLAND data
We investigate the potential of 3 kiloTon-years(kTy) of KamLAND data to
further constrain the and values compared to those
presently allowed by existing KamLAND and global solar data. We study the
extent, dependence and characteristics of this sensitivity in and around the
two parts of the LMA region that are currently allowed. Our analysis with 3 kTy
simulated spectra shows that KamLAND spectrum data by itself can constrain
with high precision. Combining the spectrum with global solar data
further tightens the constraints on allowed values of and
. We also study the effects of future neutral current data with a
total error of 7% from the Sudbury Neutrino Observatory. We find that these
future measurements offer the potential of considerable precision in
determining the oscillation parameters (specially the mass parameter).Comment: 16 pages, to appear in J Phys.
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
MSW mediated neutrino decay and the solar neutrino problem
We investigate the solar neutrino problem assuming simultaneous presence of
MSW transitions in the sun and neutrino decay on the way from sun to earth. We
do a global -analysis of the data on total rates in Cl, Ga and
Superkamiokande (SK) experiments and the SK day-night spectrum data and
determine the changes in the allowed region in the \dm - \tan^2\theta plane
in presence of decay. We also discuss the implications for unstable neutrinos
in the SNO experiment.Comment: Final version to appear in Phys. Rev.
Signature of sterile species in atmospheric neutrino data at neutrino telescopes
The MiniBooNE results have still not been able to comprehensively rule out
the oscillation interpretation of the LSND experiment. So far the so-called
short baseline experiments with energy in the MeV range and baseline of few
meters have been probing the existence of sterile neutrinos. We show how
signatures of these extra sterile states could be obtained in TeV energy range
atmospheric neutrinos travelling distances of thousands of kilometers.
Atmospheric neutrinos in the TeV range would be detected by the upcoming
neutrino telescopes. Of course vacuum oscillations of these neutrinos would be
very small. However, we show that resonant matter effects inside the Earth
could enhance these very tiny oscillations into near-maximal transitions, which
should be hard to miss. We show that imprint of sterile neutrinos could be
unambiguously obtained in this high energy atmospheric neutrino event sample.
Not only would neutrino telescopes tell the presence of sterile neutrinos, it
should also be possible for them to distinguish between the different possible
mass and mixing scenarios with additional sterile states.Comment: 26 pages, 11 figures, Version to appear in JHE
Progress in neutrino oscillation searches and their implications
Neutrino Oscillation, in which a given flavour of neutrino transforms into
another is a powerful tool for probing small neutrino masses. The intrinsic
neutrino properties involved are neutrino mass squared difference
and the mixing angle in vacuum . In this talk I will summarize the
progress that we have achieved in our search for neutrino oscillation with
special emphasis on the recent results from the Sudbury Neutrino Observatory
(SNO) on the measurement of solar neutrino fluxes. I will outline the current
bounds on the neutrino masses and mixing parameters and discuss the major
physics goals of future neutrino experiments in the context of the present
picture.Comment: Plenary Talk, WHEPP-7, January 2002, published in Pramana, Vol. 60,
261, 200