Tau neutrino magnetic moments from the Super-Kamiokande and ν\nu e-scattering data

Combined results on $\nu_{\mu}\to \nu_{\tau}$ oscillations and $\nu e$-scattering from the Super-Kamiokande and LAMPF experiments, respectively, limit the Dirac $\nu_{\tau}$ diagonal magnetic moment to $\mu_{\nu_{\tau}} < 1.9\times 10^{-9} \mu_{B}$. For the scheme with 3 Majorana neutrinos the LAMPF results allow the limitation of effective $\nu_{\tau}$ magnetic moment to $\mu_{\nu_{\tau}} < 7.6 \times 10^{-10}\mu_{B}$. 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 $\mu_{\nu_{\tau}} < 1.3\times 10^{-7} \mu_{B}$ for the case of $\nu_{\mu}\to \nu_{\tau}$ 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 $\nu\bar{\nu}\to\gamma_{l}\gamma_{l}$. 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, $\alpha_{l} < 5.4 \times 10^{-11}$. Under certain assumptions about $\gamma_{l}$ - trapping conditions we find that the region of $\alpha_{l} = 10^{-8} - 10^{-7}$ might be of interest for an experimental search for leptonic photons.Comment: 6 pages, AmSTex, LaTex. The limits are revised for neutrino chemical potential $\mu$ = 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 π0(η)→γ+X\pi^{0}(\eta)\to\gamma + X decays in neutrino experiments

It is shown that a new light gauge boson $X$ which might be produced in the decays of pseudoscalar mesons $\pi^{0}(\eta)\to\gamma + X$ could be effectively searched for in neutrino experiments via the Primakoff effect, in the process of $X + Z\to \pi^{0}(\eta) + Z$ conversion in the external Coulomb field of a nucleus. An estimate of the $X\to \pi^{0}$ 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 $SU(2)_L$ 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