Plasma-induced neutrino helicity flip in a supernova core and a constraint on the Dirac neutrino magnetic moment

We investigate the neutrino helicity flip under supernova core conditions, where the left-handed neutrinos being produced can be converted into right-handed neutrinos sterile with respect to weak interactions owing to the interaction of the magnetic moments with plasma electrons and protons. In calculating the probability for the conversion neutrino scattering by plasma components, we take into account the polarization effects attributable to both electrons and protons in the photon propagator. Based on realistic models with radial distributions and time evolution of physical parameters in a supernova core, we have obtained upper limits on the Dirac neutrino magnetic moment averaged over flavors and time from the condition that the influence of the right-handed neutrino emission on the total cooling time scale should be limited.     

Electron-positron pair generation by a neutrino in a magnetic field

The probability of generation of an e⁺ e^– pair by a neutrino moving in a magnetic field is calculated in the low energy approximation of the Weinberg-Salam model with consideration of electron and positron spin states.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 30–34, August, 1983.The authors thank A. A. Sokolov forhis kind evaluation of the study.     

Scattering of a neutrino by an electron in a magnetic field

An expression for the scattering cross-section of a neutrino by an electron in a magnetic field is obtained. The calculation is done using the exact solutions of the Dirac equation in a magnetic field in the low-energy approximation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No, 9, pp. 35–38, September, 1982.     

On the possible existence of a neutrino pulsar

If the neutrino has a magnetic moment in the interval 10⁻¹³μ_B < μ _ν < 10⁻¹² μ_B and if a magnetic field of strength about 10¹⁴ G exists in the supernova envelope, the effect of a pulsation of a neutrino signal from a supernova may arise owing to a ν _L → ν _R resonance transition in the envelope magnetic field.     

Radiative neutrino decay in a strong magnetic field

The radiative decay of neutrinos in a strong magnetic field that have relatively high energies, E ? m _e , is studied with allowance for positronium contribution to the photon polarization operator in the vicinity of the cyclotron resonance. It is shown that the probability for the process ν → νγ increases substantially upon taking into account the positronium contribution.     

Temperature shift of neutrino mass in a magnetic field

The temperature shift of the neutrino mass in a constant magnetic field is calculated within the framework of the Weinberg-Salam model. The cases of weak field and low and high temperatures are considered. The contribution to the anomalous magnetic moment of the neutrino is determined. The imaginary component of the mass correction describing the reaction of decay and W-boson formation is analyzed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–6, December, 1987.     

On the importance of low-energy beta beams for supernova neutrino physics

We argue that isotropization and, consequently, thermalization of the system of gluons and quarks produced in an ultrarelativistic heavy-ion collision does not follow from Feynman diagram analysis to any order in the coupling constant. We conclude that the apparent thermalization of quarks and gluons, leading to success of perfect fluid hydrodynamics in describing heavy-ion collisions at RHIC, can only be attributed to the non-perturbative QCD effects not captured by Feynman diagrams. We proceed by modeling these non-pertrubative thermalization effects using viscous hydrodynamics. We point out that matching Color Glass Condensate inital conditions with viscous hydrodynamics leads to a continuous evolution of all the components of the energy-momentum tensor and, unlike the case of ideal hydrodynamics, does not give rise to a discontinuity in the longitudinal pressure. An important consequence of such a matching is a relationship between the thermalization time and shear viscosity: we observe that small viscosity leads to short thermalization time.     

Self-induced suppression of collective neutrino oscillations in a supernova

We investigate collective flavor oscillations of supernova neutrinos at late stages of the explosion. We first show that the frequently used single-angle (averaged coupling) approximation predicts oscillations close to, or perhaps even inside, the neutrinosphere, potentially invalidating the basic neutrino transport paradigm. Fortunately, we also find that the single-angle approximation breaks down in this regime; in the full multiangle calculation, the oscillations start safely outside the transport region. The new suppression effect is traced to the interplay between the dispersion in the neutrino-neutrino interactions and the vacuum oscillation term.     

Ignition of thermonuclear reactions by the neutrino radiation and supernova explosions

It is pointed out that in collapsing carbon-oxygen stars (M ? 2M_⊙) the neutrino heating initiates carbon and oxygen explosion in the stellar mantle leading to its ejection, i.e., to Supernova explosion. The main heating mechanism is the neutrino-electron scattering.     

Photoproduction of neutrino pairs on an electron in a magnetic field

The spectral-angular and spectral distributions of the probability of photoproduction of neutrino pairs on an electron in a magnetic field are calculated. The dependence of the probability of this process on the magnetic-field strength, the orientation of the electron spin in the initial and final states, and also on the direction of the circular polarization of the wave is investigated.     

Self-energy operator of a massive neutrino in an external magnetic field

The effect of the magnetic field on the properties of a massive neutrino is analyzed. A general expression is derived in terms of the self-energy operator of the neutrino in an external magnetic field of arbitrary strength. This expression is valid for any relationship between the masses of the neutrino, a charged lepton, and a W-boson. An anomalous magnetic moment of a standard neutrino is investigated. The probability of massive neutrino decay into a W-boson and a charged lepton is calculated for various values of the magnetic field strength.     

Coherent development of neutrino flavor in the supernova environment

We calculate coherent neutrino and antineutrino flavor transformation in the supernova environment, for the first time including self-consistent coupling of intersecting neutrino and antineutrino trajectories. For neutrino mass-squared difference /deltam2/ = 3 x 10(-3) eV2 we find that in the normal (inverted) mass hierarchy the more tangentially-propagating (radially-propagating) neutrinos and antineutrinos can initiate collective, simultaneous medium-enhanced flavor conversion of these particles across broad ranges of energy and propagation direction. Accompanying alterations in neutrino and antineutrino energy spectra and fluxes could affect supernova nucleosynthesis and the expected neutrino signal.     

Inelastic neutrino reactions with light nuclei in a core-collapse supernova

In view of its possible role in a core-collapse supernova and in the subsequent nucleosynthesis, inelastic neutrino scattering with A = 3,4 nuclei is calculated. The predicted cross-sections result from an ab-initio calculation using microscopic two- and three-nucleon interaction and meson-exchange currents.     

High energy neutrino absorption by W production in a strong magnetic field

An influence of a strong external magnetic field on the neutrino self-energy operator is investigated. The width of the neutrino decay into the electron and W boson, and the mean free path of an ultra-high energy neutrino in a strong magnetic field are calculated. A kind of energy cutoff for neutrinos propagating in a strong field is defined.     

Annihilation of a neutrino pair into a muon-positron pair in a magnetic field

The cross section for the process $\nu _\mu + \bar \nu _e \to \mu ^ - + e^ + $ in a constant magnetic field is calculated with allowance for muon and positron polarizations. The asymptotic behavior of the cross section as a function of the kinematical and the field parameter is investigated in the case where a high-energy neutrino (antineutrino) is scattered by a low-energy antineutrino (neutrino). The effect of a weak field is especially important near the threshold for the free process. The spectrum and the total cross section for the process in a strong field differ markedly from the corresponding characteristics of the free process. Possible astrophysical applications are considered.     

Inverted hierarchy of neutrino masses disfavored by supernova 1987A

We discuss the flavor conversion of supernova neutrinos in the three-flavor mixing scheme of neutrinos. We point out that by neutrino observation from supernova one can discriminate the inverted hierarchy of neutrino masses from the normal one if s₁₃²≳a few×10⁻⁴, irrespective of which oscillation solution to the solar neutrino problem is realized in nature. We perform an analysis of data of SN1987A and obtain a strong indication that the inverted mass hierarchy is disfavored unless s₁₃²≲a few×10⁻⁴.     

Energy of neutrino radiation in beta decay in a quantizing magnetic field

Beta decay in a quantizing magnetic field is studied, in conditions where the influence of the temperature and density of the electron gas is significant. It is shown that the expressions for the probability W and power of neutrino emission E_v in conditions of degeneracy include a nonlinear dependence on the parameter H/H_c; for field values at which quantum states of the electron with n 0 are possible, they contain both monotonic and oscillating components. With increase in the field, the oscillations of W and E_v vanish. In the limit of high temperatures T mc² the oscillating corrections are considerably reduced.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 84–88, April, 1989.It remains to thank I. M. Ternov, B. A. Lysov, and A. P. Krylov for useful discussions.