151 research outputs found
Another possible way to determine the Neutrino Mass Hierarchy
We show that by combining high precision measurements of the atmospheric
delta m^2 in both the electron and muon neutrino (or anti-neutrino)
disappearance channels one can determine the neutrino mass hierarchy. The
required precision is a very challenging fraction of one per cent for both
measurements. At even higher precision, sensitivity to the cosine of the CP
violating phase is also possible. This method for determining the mass
hierarchy of the neutrino sector does not depend on matter effects.Comment: 12 pages, 3 postscript figures, late
Analytic Calculation of Neutrino Mass Eigenvalues
Implicaion of the neutrino oscillation search for the neutrino mass square
difference and mixing are discussed. We have considered the effective majorana
mass m_{ee}, related for \beta\beta_{0\nu}decay. We find limits for neutrino
mass eigen value m_{i} in the different neutrino mass spectrum,which explain
the different neutrino data.Comment: 10 page
SO(3) Gauge Symmetry and Nearly Tri-bimaximal Neutrino Mixing
In this note I mainly focus on the neutrino physics part in my talk and
report the most recent progress made in \cite{YLW0}. It is seen that the
Majorana features of neutrinos and SO(3) gauge flavor symmetry can
simultaneously explain the smallness of neutrino masses and nearly
tri-bimaximal neutrino mixing when combining together with the mechanism of
approximate global U(1) family symmetry. The mixing angle and
CP-violating phase are in general nonzero and testable experimentally at the
allowed sensitivity. The model also predicts the existence of vector-like
Majorana neutrinos and charged leptons as well as new Higgs bosons, some of
them can be light and explored at the LHC and ILC.Comment: 8 pages, invited talk, contribute to the Proceedings of the 4th
International Conference on Flavor Physics (ICFP2007
Search for a Lorentz invariance violation contribution in atmospheric neutrino oscillations using MACRO data
Neutrino-induced upward-going muons in MACRO have been analysed in terms of
relativity principles violating effects, keeping standard mass-induced
atmospheric neutrino oscillations as the dominant source of nu_mu -> nu_tau
transitions. The data disfavor these exotic possibilities even at a
sub-dominant level, and stringent 90% C.L. limits are placed on the Lorentz
invariance violation parameter |Delta v| < 6 * 10^(-24) at sin2theta_v = 0 and
|Delta v| < 2.5--5 * 10^(-26) at sin2theta_v = +/-1. These limits can also be
re-interpreted as upper bounds on the parameters describing violation of the
Equivalence Principle.Comment: 8 pages, 2 figures, submitted to Physics Letters
Solutions to large B and L breaking in the Randall-Sundrum model
The stability of proton and neutrino masses are discussed in the
Randall-Sundrum model. We show that relevant operators should be suppressed, if
the hierarchical Yukawa matrices are explained only by configurations of
wavefunctions for fermions and the Higgs field along the extra dimension. We
assume a discrete gauge symmetry to suppress those operators. In the
Dirac neutrino case, there is an infinite number of symmetries which may forbid
the dangerous operators. In the Majorana neutrino case, the discrete gauge
symmetries should originate from gauge symmetries which are broken on
the Planck brane. We also comment on the oscillation as a
phenomenon which can distinguish those discrete gauge symmetries.Comment: 12 pages, No figures, Added reference
Self-shielding effect of a single phase liquid xenon detector for direct dark matter search
Liquid xenon is a suitable material for a dark matter search. For future
large scale experiments, single phase detectors are attractive due to their
simple configuration and scalability. However, in order to reduce backgrounds,
they need to fully rely on liquid xenon's self-shielding property. A prototype
detector was developed at Kamioka Observatory to establish vertex and energy
reconstruction methods and to demonstrate the self-shielding power against
gamma rays from outside of the detector. Sufficient self-shielding power for
future experiments was obtained.Comment: 8 pages, 8 figure
Search for Radiative Decays of Cosmic Background Neutrino using Cosmic Infrared Background Energy Spectrum
We propose to search for the neutrino radiative decay by fitting a photon
energy spectrum of the cosmic infrared background to a sum of the photon energy
spectrum from the neutrino radiative decay and a continuum. By comparing the
present cosmic infrared background energy spectrum observed by AKARI and
Spitzer to the photon energy spectrum expected from neutrino radiative decay
with a maximum likelihood method, we obatined a lifetime lower limit of to years at 95% confidence level for the
third generation neutrino in the mass range between 50 \mmev
and 150 \mmev under the present constraints by the neutrino oscillation
measurements. In the left-right symmetric model, the minimum lifetime of
is predicted to be years for of 50 \mmev. We
studied the feasibility of the observation of the neutrino radiative decay with
a lifetime of years, by measuring a continuous energy
spectrum of the cosmic infrared background
The See-Saw Mechanism, Neutrino Yukawa Couplings, LFV Decays l_i to l_j + gamma and Leptogenesis
The LFV charged lepton decays mu to e + gamma, tau to e + gamma and tau to mu
+ gamma and thermal leptogenesis are analysed in the MSSM with see-saw
mechanism of neutrino mass generation and soft SUSY breaking with universal
boundary conditions. The case of hierarchical heavy Majorana neutrino mass
spectrum, M_1 10^9
GeV. Considering the natural range of values of the heaviest right-handed
Majorana neutrino mass, M_3 > 5*10^{13} GeV, and assuming that the soft SUSY
breaking universal gaugino and/or scalar masses have values in the range of few
100 GeV, we derive the combined constraints, which the existing stringent upper
limit on the mu to e + gamma decay rate and the requirement of successful
thermal leptogenesis impose on the neutrino Yukawa couplings, heavy Majorana
neutrino masses and SUSY parameters. Results for the three possible types of
light neutrino mass spectrum -- normal and inverted hierarchical and
quasi-degenerate -- are obtained.Comment: 25 pages, 9 figures; typos corrected, few clarifying comments and one
figure added; version submitted for publicatio
Determination of the atmospheric neutrino fluxes from experimental data
The precise knowledge of the atmospheric neutrino fluxes is a key ingredient
in the interpretation of the results from any atmospheric neutrino experiment.
In the standard atmospheric neutrino data analysis, these fluxes are
theoretical inputs obtained from sophisticated numerical calculations. In this
contribution we present an alternative approach to the determination of the
atmospheric neutrino fluxes based on the direct extraction from the
experimental data on neutrino event rates.Comment: 4 pages, 3 figs, to appear in the proceedings of the Multi-Messenger
Approach to High-Energy Gamma-Ray Sources Conference, Barcelona July 200
A search for periodic modulations of the solar neutrino flux in Super-Kamiokande-I
A search for periodic modulations of the solar neutrino flux was performed
using the Super-Kamiokande-I data taken from May 31st, 1996 to July 15th, 2001.
The detector's capability of measuring the exact time of events, combined with
a relatively high yield of solar neutrino events, allows a search for
short-time variations in the observed flux. We employed the Lomb test to look
for periodic modulations of the observed solar neutrino flux. The obtained
periodogram is consistent with statistical fluctuation and no significant
periodicity was found
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