150 research outputs found
Tau neutrino magnetic moments from the Super-Kamiokande and e-scattering data
Combined results on oscillations and -scattering from the Super-Kamiokande and LAMPF experiments, respectively,
limit the Dirac diagonal magnetic moment to . For the scheme with 3 Majorana neutrinos the LAMPF
results allow the limitation of effective magnetic moment to
. The moments in the scheme with
additional Majorana light sterile neutrinos as well as experiments on
stimulated radiative neutrino conversion are also discussed.Comment: 12 pages, To appear in Phys. Lett.
New limits on radiative sterile neutrino decays from a search for single photons in neutrino interactions
It has been recently shown that excess events observed by the LSND and
MiniBooNE neutrino experiments could be interpreted as a signal from the
radiative decay of a heavy sterile neutrino \nu_h produced in \nu_\mu neutral
current-like interactions. If the \nu_h exist, it would be also produced by the
\nu_\mu beam from the CERN SPS in the neutrino beam line shielding. The \nu_h's
would penetrate the shielding and be observed through the decay \nu_h -> \nu
\gamma, followed by the photon conversion into e+e- pair in the active target
of the NOMAD detector. The \nu_h's could be also produced in the iron of the
magnetic spectrometer of the CHORUS detector, located just in front of NOMAD.
Considering these two sources of \nu_h's we set new constraints on \nu_h
properties and exclude part of the LSND/MiniBooNE \nu_h parameter space using
bounds on single photons production in neutrino reactions recently reported by
the NOMAD collaboration. We find that broad bands in the parameter space are
still open for more sensitive searches for the \nu_h in future neutrino
experiments.Comment: 10 pages, 5 figures. Revised version to appear in PLB. Discussion of
dominant NC-like production of \nu_h's adde
Bound on the tau neutrino magnetic moment from the Super-Kamiokande data
It is shown that recent results from the Super-Kamiokande detector constrain
the tau neutrino diagonal magnetic moment to for the case of interpretation of
the atmospheric neutrino anomaly. It is pointed out that the large magnetic
moment of the tau neutrino could affect further understanding of the origin of
the anomaly.Comment: 7 pages, LaTex. To appear in Phys.Lett.
Bounds on neutrino magnetic moment tensor from solar neutrinos
Solar neutrinos with non-zero magnetic moments will contribute to the
electron scattering rates in the Super-Kamiokande experiment. The magnetic
moment scattering events in Super-K can be accommodated in the standard VO or
MSW solutions by a change of the parameter space of mass square difference and
mixing angle-but the shifted neutrino parameters obtained from Super-K will
(for some values of neutrino magnetic moments) become incompatible with the
fits from SNO, Gallium and Chlorine experiments. We compute the upper bounds on
the Dirac and Majorana magnetic moments of solar neutrinos by simultaneously
fitting all the observed solar neutrino rates. The bounds the magnetic moment
matrix elements are of the order of 10^{-10} Bohr magnetron.Comment: 9 pages latex file with 6 figures; References added, typos corrected,
matches version to appear in Phys Rev
Can the mirror world explain the ortho-positronium lifetime puzzle?
We suggest that the discrepant lifetime measurements of ortho-positronium can
be explained by ortho-positronium oscillations into mirror ortho-positronium.
This explanation can be tested in future vacuum experiments.Comment: about 6 pages, Latex, to appear in Phys.Lett.
Limits on leptonic photon interactions from SN1987a
If massless leptonic photons associated to electron, muon or tau leptonic
number exist they would have been emitted from supernova 1987a via the
annihilation process . By requiring that
this process does not carry away most of the energy that can be radiated by the
supernova we obtain an upper limit on the leptonic photon coupling constants,
. Under certain assumptions about
- trapping conditions we find that the region of might be of interest for an experimental search for leptonic
photons.Comment: 6 pages, AmSTex, LaTex. The limits are revised for neutrino chemical
potential = 0. The new limits do not differ significantly from the
original one. To be published in Phys.Lett.
On search for a new light gauge boson from decays in neutrino experiments
It is shown that a new light gauge boson which might be produced in the
decays of pseudoscalar mesons could be effectively
searched for in neutrino experiments via the Primakoff effect, in the process
of conversion in the external Coulomb field of a
nucleus. An estimate of the conversion rate for the NOMAD
neutrino detector at CERN is given.Comment: 9 pages, 2 figures, LaTex. Submitted to Phys. Lett.
Search for an exotic three-body decay of orthopositronium
We report on a direct search for a three-body decay of the orthopositronium
into a photon and two penetrating particles, o-Ps -> gamma + X1 + X2. The
existence of this decay could explain the discrepancy between the measured and
the predicted values of the orthopositronium decay rate. From the analysis of
the collected data a single candidate event is found, consistent with the
expected background. This allows to set an upper limit on the branching ratio <
4.4 \times 10^{-5} (at the 90% confidence level), for the photon energy in the
range from 40 keV < E_gamma< 400 keV and for mass values in the kinematical
range 0
gamma + X1 + X2 decay mode as the origin of the discrepancy.Comment: 9 pages, 3 figure
Neutrino Oscillations in a Supersymmetric SO(10) Model with Type-III See-Saw Mechanism
The neutrino oscillations are studied in the framework of the minimal
supersymmetric SO(10) model with Type-III see-saw mechanism by additionally
introducing a number of SO(10) singlet neutrinos. The light Majorana neutrino
mass matrix is given by a combination of those of the singlet neutrinos and the
active neutrinos. The minimal SO(10) model gives an unambiguous Dirac
neutrino mass matrix, which enables us to predict the masses and the other
parameters for the singlet neutrinos. These predicted masses take the values
accessible and testable by near future collider experiments under the
reasonable assumptions. More comprehensive calculations on these parameters are
also given.Comment: 14 pages, 5 figures; the version to appear in JHE
Searching for energetic cosmic axions in a laboratory experiment: testing the PVLAS anomaly
Astrophysical sources of energetic gamma rays provide the right conditions
for maximal mixing between (pseudo)scalar (axion-like) particles and photons if
their coupling is as strong as suggested by the PVLAS claim. This is
independent of whether or not the axion interaction is standard at all energies
or becomes supressed in the extreme conditions of the stellar interior. The
flux of such particles through the Earth could be observed using a metre long,
Tesla strength superconducting solenoid thus testing the axion interpretation
of the PVLAS anomaly. The rate of events in CAST caused by axions from the Crab
pulsar is also estimated for the PVLAS-favoured parameters.Comment: 5 pages, 3 figur
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