E.Kh. Akhmedov

Resonant Amplification of Neutrino Spin Rotation in Matter and the Solar Neutrino Problem

Abstract It is shown that in the presence of matter there can occur resonant amplification of the flavor-changing neutrino spin rotation in transverse magnetic fields, which is roughly analogous to the Mikheyev-Smirnov-Wolfenstein effect in neutrino oscillations. Possible consequences for solar neutrinos are briefly discussed.

Planck scale effects on the majoron

Abstract The hypothesis that non-perturbative gravitational effects lead to explicit breaking of global symmetries is considered in the context of majoron models. We find that the nonvanishing majoron mass generated by these effects can overclose the universe unless the massive majoron is unstable. The cosmological mass density constraints can then be satisfied only if V BL V BL is the scale of B − L symmetry breaking.

Implications of gallium solar neutrino data for the resonant spin flavor precession scenario

Abstract We consider the implications of the recent results of SAGE and GALLEX experiments for the solution of the solar neutrino problem in the framework of the resonant neutrino spin-flavor precession scenario. It is shown that this scenario is consistent with all the existing solar neutrino data including the gallium results. The quality of the fit of the data depends crucially on the magnetic field profile used which makes it possible to get information about the magnetic field in the solar interior. In particular, the magnetic field in the core of the sun must not be too strong (⪅ 3 × 10 6 G ). The detection rate in the gallium detectors turns out to be especially sensitive to the magnitude of Δm 2 . Predictions for forthcoming solar neutrino experiments are made.

Antineutrinos from the sun

Abstract Various mechanisms are discussed by which the sun could emit electron antineutrinos v e in addition to neutrinos V e , special attention being paid to the neutrino oscillations+spin-flavor precession scenario. For the latter, the probabilities of v e → v e conversion in the sun are calculated and experimental consequences are discussed. It is shown that this scenario can be distinguished from other v e -producing mechanisms by its unique prediction of time variations of the v e flux in direct correlation with solar activity, and also due to different consequences for experiments based on neutral-current mediated reactions.

Oscillations-assisted resonant spin-flavor precession and time variations of the solar-neutrino flux

Abstract We consider the combined effect of the resonant spin-flavor precession (RSFP) and resonant oscillations of neutrinos in the convective zone of the sun. It is shown that although the oscillations cannot give rise to the apparent time variations of the solar neutrino flux in the 37Cl experiment, they can efficiently assist the RSFP to do so. As a result, smaller values of the neutrino transition magnetic moments are required, which are compatible with the recently derived astrophysical upper bound. We also remark on new experimental results on solar neutrinos.

Resonant neutrino spin-flip transitions in twisting magnetic fields

We examine here in detail the dynamics of neutrino spin-flip transitions in twisting magnetic fields. The properties of various resonant conversions induced by field rotation are considered. The suppression factors for solarveL due to spin-flip transitions in twisting magnetic fields are calculated, and possible implications for solar neutrino experiments are discussed.

Implications of Majorana neutrino transition magnetic moments for neutrino signals from supernovae

We study resonant neutrino oscillations (RNO) and resonant spin-flavor precession (RSFP) of Majorana neutrinos inside supernovae. The response of H2O and D2O detectors to supernova neutrinos is calculated for the following scenarios: (i) standard model; (ii) RNO; (iii) RSFP, and (iv) RNO + RSFP. For the H2O detectors, event numbers for both the Kamiokande II and IMB detection efficiencies are calculated. It is shown that for sufficiently large H2O detectors (such as the planned Super-Kamiokande one) the combined analysis of the isotropic/directional event-number ratio and prompt neutronization burst signal will enable one to distinguish between all the considered possibilities provided the distance to supernova is less than 10 kpc. Even more rich and conclusive information may be reached by using the D2O detector since it will allow one to observe the neutrinos via two charged-current reaction modes and a neutral-current mode in addition to the ν-e scattering.

Three-Flavour Effects and CP- and T-Violation in Neutrino Oscillations

Some theoretical aspects of 3-flavour (3f) neutrino oscillations are reviewed. These include: general properties of 3f oscillation probabilities; matter effects in ?? ?? oscillations; 3f effects in oscillations of solar, atmospheric, reactor and supernova neutrinos and in accelerator long-baseline experiments; CP and T violation in neutrino oscillations in vacuum and in matter, and the problem of Ue3.

S WAVE PION NUCLEON INTERACTION AND PCAC IN NUCLEAR MATTER

It is shown that the pion-nucleon σM-term contribution to the S-wave π-N interaction leads to a modification of the PCAC hypothesis in nuclear matter. Some experiments that enable one to obain directly the pion-nucleon σ-term, without any extrapolation to unphysical values of the kinematical variables, are discussed.

Axial currents in nuclei in the framework of the sigma model

Abstract The renormalization of the axial-vector coupling constant in nuclear matter due to the scalar 〈 Ψ Ψ〉 condensate suppression is considered in the framework of the modified sigma model. The nucleon effective mass and the pion decay constant in nuclear matter are also calculated.