798 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 $\Delta m^2_{solar}$ and the mixing angle $\theta_{solar}$
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 $\theta_{solar}$
sensitivity by a large amount.Comment: Talk given at 4th International Conference on Nonaccelerator New
Physics (NANP 03), Dubna, Russia, 23-28 Jun 200

### What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly

We investigate how the anticipated neutral current rate from $SNO$ will
sharpen our understanding of the solar neutrino anomaly. Quantitative analyses
are performed with representative values of this rate in the expected range of
$0.8 - 1.2$. This would provide a $5 - 10 \sigma$ signal for $\nu_e$ transition
into a state containing an active neutrino component. Assuming this state to be
purely active one can estimate both the $^8B$ neutrino flux and the $\nu_e$
survival probability to a much higher precision than currently possible.
Finally the measured value of the $NC$ rate will have profound implications for
the mass and mixing parameters of the solar neutrino oscillation solution.Comment: Brief discussion on the first NC result from SNO added; final version
to be published in the MPL

### Lepton Masses in a Minimal Model with Triplet Higgs Bosons and $S_3$ Flavor Symmetry

Viable neutrino and charged lepton masses and mixings are obtained by
imposing a $S_3 \times Z_4 \times Z_3$ flavor symmetry in a model with a few
additional Higgs. We use two $SU(2)_L$ triplet Higgs which are arranged as a
doublet of $S_3$, and standard model singlet Higgs which are also put as
doublets of $S_3$. We break the $S_3$ symmetry in this minimal model by giving
vacuum expectation values (VEV) to the additional Higgs fields. Dictated by the
minimum condition for the scalar potential, we obtain certain VEV alignments
which allow us to maintain $\mu-\tau$ symmetry in the neutrino sector, while
breaking it maximally for the charged leptons. This helps us to simultaneously
explain the hierarchical charged lepton masses, and the neutrino masses and
mixings. In particular, we obtain maximal $\theta_{23}$ and zero $\theta_{13}$.
We allow for a mild breaking of the $\mu-\tau$ symmetry for the neutrinos and
study the phenomenology. We give predictions for $\theta_{13}$ and the CP
violating Jarlskog invariant $J_{CP}$, as a function of the $\mu-\tau$ symmetry
breaking parameter. We also discuss possible collider signatures and
phenomenology associated with lepton flavor violating processes.Comment: 29 pages, 5 figures. Version to be appeared in PRD. Phenomenology of
Lepton flavor violation and possible collider signatures of this model have
been include

### Global oscillation analysis of solar neutrino data with helioseismically constrained fluxes

A seismic model for the Sun calculated using the accurate helioseismic data
predicts a lower $^{8}{B}$ neutrino flux as compared to the standard solar
model (SSM). However, there persists a discrepancy between the predicted and
measured neutrino fluxes and it seems necessary to invoke neutrino oscillations
to explain the measurements. In this work, we have performed a global, unified
oscillation analysis of the latest solar neutrino data (including the results
of SNO charged current rate) using the seismic model fluxes as theoretical
predictions. We determine the best-fit values of the neutrino oscillation
parameters and the $\chi^2_{\mathrm min}$ for both $\nu_e-\nu_{\mathrm active}$
and $\nu_e -\nu_{\mathrm sterile}$ cases and present the allowed parameter
regions in the $\Delta m^2 - \tan^2 \theta$ plane for $\nu_e-\nu_{\mathrm
active}$ transition. The results are compared with those obtained using the
latest SSM by Bahcall and his collaborators.Comment: Version to appear in Phys. Rev.

### On Probing theta_{23} in Neutrino Telescopes

Among all neutrino mixing parameters, the atmospheric neutrino mixing angle
theta_{23} introduces the strongest variation on the flux ratios of ultra high
energy neutrinos. We investigate the potential of these flux ratio measurements
at neutrino telescopes to constrain theta_{23}. We consider astrophysical
neutrinos originating from pion, muon-damped and neutron sources and make a
comparative study of their sensitivity reach to theta_{23}. It is found that
neutron sources are most favorable for testing deviations from maximal
theta_{23}. Using a chi^2 analysis, we show in particular the power of
combining (i) different flux ratios from the same type of source, and also (ii)
combining flux ratios from different astrophysical sources. We include in our
analysis ``impure'' sources, i.e., deviations from the usually assumed initial
(1 : 2 : 0), (0 : 1 : 0) or (1 : 0 : 0) flux compositions.Comment: 17 pages, 5 figures. Added discussion on experimental errors. To
appear in PR

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