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N. V. Mikheev

Publications and source records attributed to N. V. Mikheev.

At least 37 records · Page 2Linked to original sources
arXiv2007

Plasma induced neutrino spin-flip in a supernova and new bounds on the neutrino magnetic moment

The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account in a more complete form than in earlier publications. It is shown in part that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the left-handed neutrino washing out. The best upper bound on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to 7.

hep-ph↗
arXiv2007

Plasma induced fermion spin-flip conversion f_L -> f_R + gamma

The fermion spin-flip conversion f_L -> f_R + gamma is considered, caused by the difference of the additional energies of the electroweak origin, acquired by left- and right-handed fermions (neutrino, electron) in medium. An accurate taking account of the fermion and photon dispersion in medium is performed. It is shown that the threshold arises in the process, caused by the photon (plasmon) effective mass. This threshold leaves no room for the so-called ``spin light of neutrino'' and ``spin light of electron'' in the real astrophysical situations.

hep-ph↗
arXiv2006

Comment on ``Spin light of neutrino in matter: a new type of electromagnetic radiation''

We show that a criticism made in hep-ph/0610294 against our paper Mod. Phys. Lett. A21, 1769 (2006) has no ground. We confirm that all results of investigations of the so-called ``spin light of neutrino (SL ν)'' are incorrect because of the medium influence on photon dispersion. With taking account of this influence, both the SL νradiation rate and the total power are zero for neutrinos in all real astrophysical conditions.

hep-ph↗
arXiv2006

Neutrino dispersion in external magnetic field and plasma

Neutrino dispersion properties in an active medium consisting of magnetic field and plasma are analysed. We consider in detail the contribution of a magnetic field into the neutrino self-energy operator Sigma (p). The results for this contribution were contradictory in the previous literature. For the conditions of the early universe where the background medium consists of a charge-symmetric plasma, the pure magnetic field contribution to the neutrino dispersion relation is proportional to (e B)^2 and thus comparable to the contribution of the magnetized plasma. We consider one more hypothetical effect of the active medium influence on neutrino properties, the so-called ``neutrino spin light'' discussed in the literature. We show that this effect has no physical region of realization because of the medium influence on photon dispersion.

hep-ph↗
arXiv2006

Neutrino chirality flip in a supernova and the bound on the neutrino magnetic moment

The neutrino chirality-flip process under the conditions of the supernova core is investigated in detail with the plasma polarization effects in the photon propagator taken into account. It is shown that the contribution of the proton fraction of plasma is essential. New upper bounds on the neutrino magnetic moment are obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from the limit on the averaged time of the neutrino spin-flip. The best astrophysical upper bound on the neutrino magnetic moment is improved by the factor of 3 to 7.

hep-ph↗
arXiv2006

Plasma induced neutrino radiative decay instead of neutrino spin light

The conversion nu_L -> nu_R gamma^* of a neutrino with a magnetic moment is considered, caused by the additional Wolfenstein energy acquired by a left-handed neutrino in medium, with an accurate taking account of the photon γ^* dispersion in medium. It is shown that the threshold arises in the process, caused by the photon (plasmon) effective mass. This threshold leaves no room for the so-called "neutrino spin light" in the most of astrophysical situations.

hep-ph↗
arXiv2006

Neutrino propagation in magnetized plasma

The process of neutrino propagation through an active medium consisting of magnetic field and plasma is analysed. We consider in detail the contribution of a magnetic field B into the neutrino self-energy operator Sigma (p). The results for this contribution were contradictory in the previous literature. For the conditions of the early universe where the background medium consists of a charge-symmetric plasma, the pure B-field contribution to the neutrino dispersion relation is proportional to (e B)^2 and thus comparable to the contribution of the magnetized plasma. The neutrino self-energy operator Sigma (p) is calculated also for the case of high-energy neutrinos, which corresponds to the crossed field approximation. The probability of the neutrino decay nu to e^- W^+ is calculated from the imaginary part of the Sigma (p) operator. A simple analytical result is obtained for the most interesting region of parameters which was not considered earlier. The external magnetic field contribution into the neutrino magnetic moment is calculated. The result obtained corrects the formulas existed earlier. We show qualitatively that the effect of ``neutrino spin light'' discussed in the literature has no physical region of realization because of the medium influence on photon dispersion.

hep-ph↗
arXiv2005

Field-induced interaction of a pseudoscalar particle with photon in a magnetized $e^-e^+$ plasma

The effective interaction of a pseudoscalar particle with photon in plasma with the presence of a constant uniform magnetic field is investigated. It is shown that under some physical conditions the effective coupling between pseudoscalar particle and photon does not depend on medium parameters and particles momentum. The probability of the familon decay into photon pair in a strongly magnetized degenerate ultrarelativistic plasma is calculated.

hep-ph↗
arXiv2005

Neutrino dispersion in external magnetic fields

We calculate the neutrino self-energy operator Sigma (p) in the presence of a magnetic field B. In particular, we consider the weak-field limit e B << m_\ell^2, where m_\ell is the charged-lepton mass corresponding to the neutrino flavor ν_\ell, and we consider a "moderate field" m_\ell^2 << e B << m_W^2. Our results differ substantially from the previous literature. For a moderate field, we show that it is crucial to include the contributions from all Landau levels of the intermediate charged lepton, not just the ground-state. For the conditions of the early universe where the background medium consists of a charge-symmetric plasma, the pure B-field contribution to the neutrino dispersion relation is proportional to (e B)^2 and thus comparable to the contribution of the magnetized plasma.

hep-ph↗
arXiv2003

The influence of strong magnetic field on photon-neutrino reactions

The two-photon two-neutrino interaction induced by magnetic field is investigated. In particular the processes $γγ\to ν\bar ν$ and $γ\to γν\bar ν$ are studied in the presence of strong magnetic field. An effective Lagrangian and partial amplitudes of the processes are presented. Neutrino emissivities due to the reactions $γγ\to ν\bar ν$ and $γ\to γν\bar ν$ are calculated taking into account of the photon dispersion and large radiative corrections. A comparison of the results obtained with previous estimations and another inducing mechanisms of the processes under consideration is made.

hep-ph↗
arXiv2003

General amplitude of the n - vertex one-loop process in a strong magnetic field

A general analysis of the n-vertex loop amplitude in a strong magnetic field is performed, based on the asymptotic form of the electron propagator in the field. As an example, the photon-neutrino processes are considered, where one vertex in the amplitude is of a general type, and the other vertices are of the vector type. It is shown, that for odd numbers of vertices only the SV_1 ... V_{n-1} amplitude grows linearly with the magnetic field strength, while for even numbers of vertices the linear growth takes place only in the amplitudes PV_1 ... V_{n-1}, VV_1 ... V_{n-1} and AV_1 ... V_{n-1}. The general expressions for the amplitudes of the processes gamma gamma -> nu bar nu (in the framework of the model with the effective nu nu e e - coupling of a scalar type) and gamma gamma -> nu bar nu gamma (in the framework of the Standard Model) for arbitrary energies of particles are obtained. A comparison with existing results is performed.

hep-ph↗
arXiv2003

Photon-neutrino interactions in strong magnetic field

The two-photon two-neutrino interaction induced by magnetic field is investigated. In particular the processes $γγ\to ν\bar ν$ and $γ\to γν\bar ν$ are studied in the presence of strong magnetic field. An effective Lagrangian and partial amplitudes of the processes are presented. Neutrino emissivities due to the reactions $γγ\to ν\bar ν$ and $γ\to γν\bar ν$ are calculated taking into account of the photon dispersion and large radiative corrections. A comparison of the results obtained with previous estimations and another inducing mechanisms of the processes under consideration is made.

hep-ph↗
arXiv2002

Could the process of neutrino photoproduction on nuclei, stimulated by a strong magnetic field, compete with URCA processes?

The recent studies is reported of the neutrino photoproduction on nuclei, gamma + Ze -> Ze + gamma + nu + anti-nu, in a strong magnetic field. It is shown that the catalyzing influence of the field on the process decreases essentially because of the modification of the photon dispersion properties in a strong magnetic field. Therefore, at any field magnitude, neutrino photoproduction cannot compete with the URCA processes. This conclusion contradicts a recent statement in the literature.

hep-ph↗
arXiv2002

Neutrino-electron processes in a dense magnetized plasma

The neutrino-electron scattering in a dense degenerate magnetized plasma under the conditions $μ^2 > 2eB \gg μE$ is investigated. The volume density of the neutrino energy and momentum losses due to this process are calculated. The results we have obtained demonstrate that plasma in the presence of an external magnetic field is more transparent for neutrino than non-magnetized plasma. It is shown that neutrino scattering under conditions considered does not lead to the neutrino force acting on plasma.

hep-ph↗
arXiv2002

Electron Mass Operator in a Strong Magnetic Field and Dynamical Chiral Symmetry Breaking

The electron mass operator in a strong magnetic field is calculated. The contribution of higher Landau levels of virtual electrons, along with the ground Landau level, is shown to be essential in the leading log approximation. The effect of the electron dynamical mass generation by a magnetic field is investigated. In a model with N charged fermions, it is shown that some critical number N_{cr} exists for any value of the electromagnetic coupling constant alpha, such that the fermion dynamical mass is generated with a doublet splitting for N < N_{cr}, and the dynamical mass does not arise at all for N > N_{cr}, thus leaving the chiral symmetry unbroken.

hep-ph↗
arXiv2002

Electron mass operator in a strong magnetic field

The electron mass operator in a strong magnetic field is calculated by summation of the leading log contributions in all orders of the perturbation theory. An influence of the strong field on the virtual photon polarization operator is taken into account. The contribution of higher Landau levels of virtual electrons, along with the ground Landau level, is shown to be essential in the leading log approximation.

hep-ph↗
arXiv2001

Photon-pair conversion into neutrinos in a strong magnetic field

A general analysis of the three-vertex loop amplitude in a strong magnetic field, based on the asymptotic form of the electron propagator in the field, is performed. In order to investigate the photon-neutrino process gamma gamma -> nu bar nu, the vertex combinations of the scalar-vector-vector (SVV), pseudoscalar-vector-vector (PVV), 3-vector (VVV), and axial-vector-vector-vector (AVV) types are considered. It is shown that only the SVV amplitude grows linearly with the magnetic field strength, while in the other amplitudes, PVV, VVV, and AVV, the linearly growing terms are cancelled. The process gamma gamma -> nu bar nu is investigated in the left-right-symmetric extension of the standard model of electroweak interaction, where the effective scalar nu nu e e coupling could exist. Possible astrophysical manifestations of the considered process are discussed.

hep-ph↗