22 research outputs found
Atmospheric neutrino oscillations in three-flavor neutrinos
We analyzed the atmospheric neutrino experiments of SuperKamiokande including
zenith angle dependence's using the three-flavor neutrino framework with the
hierarchy m^2_1 \approx m^2_2<<m^2_3. Taking into account the terrestrial,
solar neutrino experimental data and the atmospheric neutrino experiments
including the sub-GeV and multi-GeV data in SuperKamiokande, large angle
solution in the solar neutrino experiments is favored and the range of the mass
parameter Deltam^2_{23} is restricted between 0.08eV^2 - 2eV^2. Allowed regions
of mixing parameters are (theta_{13}<4degree, 27degree<theta_{23}< 32degree)
for Delta m_{23}^2=1eV^2 and (theta_{13}<3degree, 28degree<theta_{23}
<33degree) for Deltam_{23}^2=0.1 eV^2.Comment: 21 pages, LaTe
MiniBooNE Oscillation Results 2011
The MiniBooNE neutrino oscillation search experiment at Fermilab has recently
updated results from a search for
oscillations, using a data sample corresponding to
protons on target in anti-neutrino mode. This high statistics result represent
an increase in statistics of 52% compared to result published in 2010. An
excess of 57.7 28.5 events is observed in the energy range 200 MeV 3000 MeV. The data favor LSND-like
oscillations over a background only hypothesis at 91.1% confidence level in the
energy range 475 3000 MeV.Comment: 4 pages, 6 figures, talk given at NuFact 2011, XIIIth
InternationalWorkshop on Neutrino Factories, Super beams and Beta beams,
CERN/UNIGE, Geneva, Switzerland, August 1-6, 201
MiniBooNE Results and Neutrino Schemes with 2 sterile Neutrinos: Possible Mass Orderings and Observables related to Neutrino Masses
The MiniBooNE and LSND experiments are compatible with each other when two
sterile neutrinos are added to the three active ones. In this case there are
eight possible mass orderings. In two of them both sterile neutrinos are
heavier than the three active ones. In the next two scenarios both sterile
neutrinos are lighter than the three active ones. The remaining four scenarios
have one sterile neutrino heavier and another lighter than the three active
ones. We analyze all scenarios with respect to their predictions for
mass-related observables. These are the sum of neutrino masses as constrained
by cosmological observations, the kinematic mass parameter as measurable in the
KATRIN experiment, and the effective mass governing neutrinoless double beta
decay. It is investigated how these non-oscillation probes can distinguish
between the eight scenarios. Six of the eight possible mass orderings predict
positive signals in the KATRIN and future neutrinoless double beta decay
experiments. We also remark on scenarios with three sterile neutrinos. In
addition we make some comments on the possibility of using decays of high
energy astrophysical neutrinos to discriminate between the mass orderings in
presence of two sterile neutrinos.Comment: 33 pages, 8 figures. Comments added, to appear in JHE
Relic neutrino masses and the highest energy cosmic rays
We consider the possibility that a large fraction of the ultrahigh energy
cosmic rays are decay products of Z bosons which were produced in the
scattering of ultrahigh energy cosmic neutrinos on cosmological relic
neutrinos. We compare the observed ultrahigh energy cosmic ray spectrum with
the one predicted in the above Z-burst scenario and determine the required mass
of the heaviest relic neutrino as well as the necessary ultrahigh energy cosmic
neutrino flux via a maximum likelihood analysis. We show that the value of the
neutrino mass obtained in this way is fairly robust against variations in
presently unknown quantities, like the amount of neutrino clustering, the
universal radio background, and the extragalactic magnetic field, within their
anticipated uncertainties. Much stronger systematics arises from different
possible assumptions about the diffuse background of ordinary cosmic rays from
unresolved astrophysical sources. In the most plausible case that these
ordinary cosmic rays are protons of extragalactic origin, one is lead to a
required neutrino mass in the range 0.08 eV - 1.3 eV at the 68 % confidence
level. This range narrows down considerably if a particular universal radio
background is assumed, e.g. to 0.08 eV - 0.40 eV for a large one. The required
flux of ultrahigh energy cosmic neutrinos near the resonant energy should be
detected in the near future by AMANDA, RICE, and the Pierre Auger Observatory,
otherwise the Z-burst scenario will be ruled out.Comment: 19 pages, 22 figures, REVTeX
High sensitivity GEM experiment on double beta decay of 76-Ge
The GEM project is designed for the next generation 2 beta decay experiments
with 76-Ge. One ton of ''naked'' HP Ge detectors (natural at the first GEM-I
phase and enriched in 76-Ge to 86% at the second GEM-II stage) are operating in
super-high purity liquid nitrogen contained in the Cu vacuum cryostat (sphere
with diameter 5 m). The latest is placed in the water shield. Monte Carlo
simulation evidently shows that sensitivity of the experiment (in terms of the
T1/2 limit for neutrinoless 2 beta decay) is 10^27 yr with natural HP Ge
crystals and 10^28 yr with enriched ones. These bounds corresponds to the
restrictions on the neutrino mass less than 0.05 eV and 0.015 eV with natural
and enriched detectors, respectively. Besides, the GEM-I set up could advance
the current best limits on the existence of neutralinos - as dark matter
candidates - by three order of magnitudes, and at the same time would be able
to identify unambiguously the dark matter signal by detection of its seasonal
modulation.Comment: LaTeX, 20 pages, 4 figure
Future Oscillation Experiments and Present Data
Our goal in this paper is to examine the discovery potential of laboratory
experiments searching for the oscillation , in the light of recent data on solar and atmospheric neutrino
experiments, which we analyse together with the most restrictive results from
laboratory experiments on neutrino oscillations. In order to explain
simultaneously present results we use a four-neutrino framework, with an
additional sterile neutrino. Our predictions are rather pessimistic for the
upcoming experiments NOMAD and CHORUS, which, we find, are able to explore only
a small area of the oscillation parameter space. On the other hand, the
discovery potential of future experiments is much larger. We consider three
examples. E803, which is approved to operate in the future Fermilab main
injector beam line, MINOS, a proposed long-baseline experiment also using the
Fermilab beam, and NAUSICAA, an improved detector which improves by an order of
magnitude the performance of CHORUS/NOMAD and can be operated either at CERN or
at Fermilab beams. We find that those experiments can cover a very substantial
fraction of the oscillation parameter space, having thus a very good chance of
discovering and oscillation modes.Comment: Latex file using ReVTeX and epsifig.sty. 40 Pages. Revised version
includes new references and changed Fig.
Measurements of Charged Current Reactions of on
Charged Current reactions of on have been studied using a
decay-at-rest beam at the Los Alamos Neutron Science Center.
The cross section for the exclusive reaction
was measured to be cm. The observed
energy dependence of the cross section and angular distribution of the outgoing
electron agree well with theoretical expectations. Measurements are also
presented for inclusive transitions to excited states,
and compared with theoretical expectations. The
measured cross section, cm, is somewhat
lower than previous measurements and than a continuum random phase
approximation calculation. It is in better agreement with a recent shell model
calculation.Comment: 34 pages, 18 figures, accepted to PRC, replaced with the accepted on
A complete solution to neutrino mixing
Deviations from expectations have been claimed for solar, atmospheric and
high energy prompt neutrinos from charm decay. This information, supplemented
only by the existing very good upper limits for oscillations of the
at accelerator energies, is used as input to a phenomenological three-flavour
analysis of neutrino mixing. The solution found is unique and completely
determines the mass eigenstates as well as the mixing matrix relating mass and
flavour eigenstates. Assuming the mass eigenstates to follow the hierarchy
, their values are found to be
eV, eV, eV. These masses are
in agreement with the leptonic quadratic hierarchy of the see-saw model and
large enough to render energy-independent any oscillation-induced phenomenon in
solar neutrino physics observable on Earth. This possibility is not excluded by
the present knowledge of solar neutrino physics. The mixing angles are
determined to be , ,
. Small values of are typical of any solution
in which lies in the cosmological interesting region. The solution
found is not in serious contradiction with any of the present limits to the
existence of neutrino oscillations. The most relevant implications in particle
physics, astrophysics and cosmology are discussed.Comment: 17 pages, 3 figures, to be published in Astroparticle Physic
Models of Neutrino Masses and Mixings
We review theoretical ideas, problems and implications of neutrino masses and
mixing angles. We give a general discussion of schemes with three light
neutrinos. Several specific examples are analyzed in some detail, particularly
those that can be embedded into grand unified theories.Comment: 44 pages, 2 figures, version accepted for publication on the Focus
Issue on 'Neutrino Physics' edited by F.Halzen, M.Lindner and A. Suzuki, to
be published in New Journal of Physics