Neutrino decay of an axion in an external electromagnetic field

Switching on an external electromagnetic field opens a neutrino decay channel of a hypothetical pseudoscalar particle, an axion, which plays an important role in modern field theory. We obtain exact expressions in the one-loop approximation for the probability of the decay into a massless neutrino in a crossed fieldF and study the asymptotic behavior by the nature of the parameter . Moscow State Industrial University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 2, pp. 8–12, February, 1999.     

Neutrino radiative decay in N=1 supergravity theories

We show that the supersymmetrization of models where neutrinos acquire mass through the see-saw mechanism allows for tau neutrinos heavier than 15–20 MeV to decay radiatively in a cosmologically safe way (i.e. with a lifetime τ_v⩽5×10³s).     

Neutrino processes in an external active medium

Possible manifestations of the interaction of neutrinos with an active external astrophysical medium (dense plasma and strong magnetic field) owing both to the nonstandard magnetic moment of the Dirac neutrino appearing in extensions of the Standard Model and to the standard weak interaction have been analyzed.     

Neutrino transitions in an external field

In the article the transitionv _e f v is considered in a field of plane-wave type, induced by the effective values of the anomalous magnetic and electric dipole moments of massive neutrinos. The possible contribution of the given mechanism to the background of quantum mechanical oscillatory phenomena is discussed.Moscow State Correspondence Pedagogical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 31–35, January, 1993.     

Neutrino dispersion properties in an external magnetic field

The neutrino self-energy operator Σ(p) in a magnetic field is calculated for the case of high-energy neutrinos, this corresponding to the crossed field approximation. The probability of the neutrino decay ν → e ^? W ⁺ is found by using the imaginary part of the operator Σ(p). A simple analytic result is obtained in the parameter region that is the most interesting from the physical point of view and which was not considered earlier. The contribution of an external magnetic field to the neutrino magnetic moment is calculated. The result obtained here for this contribution corrects formulas available previously.     

Neutrino propagation in a medium with a magnetic field

Data on the mean multiplicity of strange hadrons produced in minimum bias proton-proton and central nucleus-nucleus collisions at momenta between 2.8 and 400 GeV/c per nucleon have been compiled. The multiplicities for nucleon-nucleon interactions were constructed. The ratios of strange particle multiplicity to participant nucleon as well as to pion multiplicity are larger for central nucleus-nucleus collisions than for nucleon-nucleon interactions at all studied energies. The data at AGS energies suggest that the latter ratio saturates with increasing masses of the colliding nuclei. The strangeness to pion multiplicity ratio observed in nucleon-nucleon interactions increases with collision energy in the whole energy range studied. A qualitatively different behaviour is observed for central nucleus-nucleus collisions: the ratio rapidly increases when going from Dubna to AGS energies and changes little between AGS and SPS energies. This change in the behaviour can be related to the increase in the entropy production observed in central nucleus-nucleus collisions at the same energy range. The results are interpreted within a statistical approach. They are consistent with the hypothesis that the Quark Gluon Plasma is created at SPS energies, the critical collision energy being between AGS and SPS energies.     

Monopole decay in a variable external field

The rate of monopole decay into a dyon and an electron in an inhomogeneous external electric field is calculated by semiclassical methods. Comparison is made to an earlier result where this quantity was calculated for a constant field. Experimental and cosmological tests are suggested. The text was submitted by the authors in English.     

Local field and radiative relaxation rate in a dielectric medium

The effect of macroscopic parameters of a substance on the optical characteristics of impurity particles is investigated. A generalized control equation is derived for two-level emitters forming an ensemble of optical centers in a transparent dielectric medium. In this equation, the effective values of the acting pump field and the radiative relaxation rate of an optical center are taken into account. The formalism developed here is a completely microscopic approach based on the chain of the Bogoliubov-Born-Green-Kirkwood-Yvon equations for reduced density matrices and correlation operators for material particles and modes of a quantized radiation field. The method used here makes it possible to take into account the effects of individual and collective behavior of emitters, which are associated with the presence of an intermediate medium, consistently without using phenomenological procedures. It is shown that the resultant analytic expression for the effective lifetime of the excited state of an optical center conforms with experimental data.     

Two-photon axion decay in an external electromagnetic field

The amplitude of two-photon axion decay in a crossed field is calculated, taking into account the polarization states of the photons. The decay probability and amplitude in an external electromagnetic field exceed the decay probability and amplitude in vacuum even for values of the invariant parameter greater than the small quantity m _a/m _e. Astrophysical aspects associated with this circumstance are discussed. Zh. éksp. Teor. Fiz. 115, 385–391 (February 1999)     

Inverse muon decay in a steady external field

A standard Weinberg-Salam model has been used to calculate the cross section of +e »v _e+ in steady crossed fields (EH=E ²–H ²=0). The asymptotic behavior of the cross section has been examined as a function of the kinematic and dynamic (field) invariant parameters.M. V. Lomonosov Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 106–111, December, 1992.     

Neutrino in matter and external fields

A technique for describing various processes proceeding in matter and involving neutrinos and electrons is discussed. This technique is based on “the method of exact solutions,” which implies the use of solutions to proper Dirac equations for particle wave functions in matter. Exact solutions for the neutrino and the electron in the cases of uniform nonmoving and rotating matter are discussed. On studying relativistic neutrino motion and associated neutrino-energy quantization in rotating matter, a semiclassical interpretation of particle finite motion is developed. In the general case of neutrino and electron motion in matter with varying parameters, the corresponding effective force acting on the particles is determined. The possibility of electromagnetic-wave radiation by an electron that moves in a dense neutrino flux of varying density and which is accelerated by this kind of force is predicted.     

Neutrino oscillations induced by two-loop radiative mechanism

Two-loop radiative mechanism, when combined with an U(1)_L′ symmetry generated by L_e − L_μ − L_τ (=L′), is shown to provide an estimate of Δm²/Δm²_atm εm_e/m_τ, where ε measures the U(1)_L′-breaking. Since Δm²_atm 3.5×10⁻³ eV², we find that Δm² ε10⁻⁶ eV², which will fall into the allowed region of the LOW solution to the solar neutrino problem for ε 0.1.     

Neutrino mass constraints on beta decay

Using the general connection between the upper limit on the neutrino mass and the upper limits on certain types of non-standard-model interactions that can generate loop corrections to the neutrino mass, we derive constraints on some non-standard-model d --> ue- nu interactions. When cast into limits on n --> pe- nu coupling constants, our results yield constraints on scalar and tensor weak interactions improved by more than an order of magnitude over the current experimental limits. When combined with the existing limits, our results yield absolute value(C(S)/C(V)) approximately < 5 x 10(-3), absolute value(C'(S)/C(V)) approximately < 5 x 10(-3), absolute value(C(T)/C(A)) approximately < 1.2 x 10(-2), and absolute value(C'(T)/C(A)) approximately < 1.2 x 10(-2).     

Equivalence of MTF of a turbid medium and radiative transfer field

The equivalence of the modulation transfer function (MTF) of a turbid medium and the transmitted radiance from the medium under isotropic diffuse illumination is demonstrated. MTF of a turbid medium can be fully evaluated by numerically solving a radiative transfer problem in a plane parallel medium. MTF for a homogenous single layer turbid medium is investigated as illustration. General features of the MTF in the low and high spatial frequency domains are provided through their dependence on optical thickness, single scattering albedo, asymmetrical factor, and phase function type.     

Neutrino oscillations in low density medium

We have solved the evolution equation for neutrinos in a low density medium, Vnu(e), we have found the attenuation effect: a decrease of the sensitivity to remote structures, d>l(nu)E/DeltaE, where l(nu) is the oscillation length and DeltaE/E is the energy resolution of a detector.     

Secondary photon spectra in radiative decay of an auto-ionized state in a strong field

Radiative decay of an auto-ionized state in a strong field is examined with consideration of degeneration of the atom's continuous spectrum states. It is shown that this degeneration affects the form of the spontaneous photon spectrum significantly.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 7–10, December, 1987.