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N. V. Mikheev

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

At least 73 records · Page 4Linked to original sources
arXiv1998

Axion Emission by Magnetic-Field Induced Conversion of Longitudinal Plasmons

Magnetic fields mix axions with photons, allowing for the cyclotron process e -> e + a by virtue of an intermediate plasmon even if axions do not couple to electrons at tree level. The axion and longitudinal-plasmon dispersion relations always cross for a certain wave number, leading to a resonant enhancement of this process. Even then, however, it cannot quite compete with the usual nucleon processes in a supernova core. The well-known axion window 10^{-5} eV < m_a < 10^{-2} eV remains open and axions may still constitute the cosmic dark matter.

hep-ph↗
arXiv1998

Photon decay gamma->nu anti-nu in an external magnetic field

The process of the photon decay into the neutrino - antineutrino pair in a magnetic field is investigated. The amplitude and the probability are analysed in the limits of relatively small and strong fields. The probability is suppressed by a factor (G_F m^2_e)^2 as compared with the probability of the pure electromagnetic process gamma -> e- e+. However, the process with neutrinos could play a role of an additional channel of stellar energy-loss.

hep-ph↗
arXiv1998

$a \to e^+ e^-$ decay in a model with induced coupling to leptons

The process of electron-positron pair production by axion propagating in an external magnetic field is investigated in a model with only induced axion coupling to leptons. Contributions of the lowest and higher Landau levels are analyzed. The results we have obtained demonstrate a strong catalyzing influence of the field.

hep-ph↗
arXiv1997

Field-induced axion decay $a \to e^+ e^-$ in KSVZ-model

The axion decay into electron-positron pair $a \to e^+ e^-$ is studied in an external magnetic field in KSVZ-model where axions have only induced coupling to leptons. The axion lifetime in the field decreases with energy and field strength to seconds.

hep-ph↗
arXiv1997

Neutrino transitions nu -> nu gamma, nu -> nu e+ e- in a strong magnetic field as a possible origin of cosmological gamma-burst

The high energy neutrino transitions with the photon and electron-positron pair creation in a strong magnetic field in the framework of the Standard Model are investigated. The process probabilities and the mean values of the neutrino energy and momentum loss are presented. The asymmetry of outgoing neutrinos, as a possible source of sufficient recoil ``kick'' velocity of a remnant and the emission of e+ e- pairs and gamma-quanta in a ``polar cap'' region of a remnant, as a possible origin of cosmological gamma-burst are discussed.

hep-ph↗
arXiv1997

Creation of photons and electron - positron pairs by a neutrino in a strong magnetic field

The processes of the photon and electron-positron pair production by a neutrino propagating in a strong magnetic field are investigated in the framework of the Standard Model. The process probabilities and the mean values of the neutrino energy and momentum loss are calculated. Possible astrophysical manifestations of the processes considered are briefly analysed.

hep-ph↗
arXiv1997

Radiative Transition of Massless Neutrino in Strong Magnetic Field

Radiative transition of massless neutrino $ν_l \to ν_l + γ$ ($l = e, μ, τ$) in a strong magnetic field is investigated in the framework of the Standard Model. The process probability and the mean values of the neutrino energy and momentum loss are presented. Possible astrophysical manifestation of the process considered is analysed.

hep-ph↗
arXiv1997

About an influence of external electromagneticfields on the axion decays

Some results of an external electromagnetic field influence on axion decays are presented. It is shown that the field catalyzes substantially these processes. The result describing the axion decay $a \to f \tilde f$ we have obtained can be of use to re-examine the lower limit on the axion mass in case of possible existence of strong magnetic fields at the early Universe stage.

hep-ph↗
arXiv1997

Axion decay $a \to f \tilde f$ in a strong magnetic field

The axion decay into charged fermion-antifermion pair $a ~\to f ~\tilde f$ is studied in external crossed and magnetic fields. The result we have obtained can be of use to re-examine the lower limit on the axion mass in case of possible existence of strong magnetic fields at the early Universe stage.

hep-ph↗
arXiv1997

Electromagnetic Catalysis of the Radiative Decay of the Axion

The radiative decay of the axion $a \to γγ$ is investigated in an external electromagnetic field in DFSZ model in which axion couples to both quarks and leptons at tree level. The decay probability is strongly catalyzed by the external field, namely, the field removes the main suppression caused by the smallness of the axion mass.

hep-ph↗
arXiv1997

Resonance neutrino bremsstrahlung $ν\to νγ$ in a strong magnetic field

High energy neutrino bremsstrahlung $ν\to ν+ γ$ in a strong magnetic field ($B \gg B_s$) is studied in the framework of the Standard Model (SM). A resonance probability and a four-vector of the neutrino energy and momentum loss are presented. A manifestation of the neutrino bremsstrahlung in astrophysical cataclysm of type of a supernova explosion or a merger of neutron stars, such as an possible origin of cosmological $γ$-burst is discussed.

hep-ph↗
arXiv1996

Neutrino Radiative Decay in an External Electromagnetic Field via Vector Leptoquark

The massive neutrino radiative decay $ν_i \rightarrow ν_j γ$ ($i \ne j$) is investigated within the Minimal Quark-Lepton Symmetry of the Pati-Salam type based on the $SU(4)_V \times SU(2)_L \times G_R$ group in an external constant crossed field ($\vec {\cal E} \perp \vec H$, ${\cal E}=H$). The matrix element $ΔM^{(X)}$ and the decay probability $W^{(X)}$ due to the leptoquark $X$ contribution are analysed. The effect of significant enhancement of the neutrino decay by the crossed field takes place. It is shown that the leptoquark contribution to the decay probability can dominate over the $W$-boson one in the case of strong suppression of the lepton mixing in the framework of the SM.

hep-ph↗
arXiv1996

The radiative decay of the massive neutrino in the external electromagnetic fields

The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ is investigated in the framework of the Standard Model in external electromagnetic fields of various configurations: constant crossed field, constant uniform magnetic field, plane monochromatic wave's field. The effect of significant enhancement of the neutrino decay probability by the external field (electromagnetic catalysis) is discussed. An especially strong enhancement occurs in the case of the ultrarelativistic neutrino decay, since in this case the decay probability does not contain suppression caused by the smallness of the decaying neutrino mass. The ultrarelativistic neutrino decay catalysis is significant even in a relatively weak external field ($F/F_e << 1$, where $F_e$ is the critical Schwinger value). The expression for the photon splitting probability into the neutrino pair $γ\rightarrow ν_i \barν_j$ in the wave field is given. The estimations of a number of gamma-quanta produced in a volume filled with an electromagnetic field and the neutrino lifetime in a strong magnetic field are presented.

hep-ph↗
arXiv1995

Unitary Limit on $K^0_L \to μ^+ μ^-$ and the Top Quark Mass

A brief overview of the recent measurements of the branching ratio of the rare $K_L^0 \to μ^+ μ^-$ decay in the context of their agreement with the Standard Model (SM) is given. It is shown that KEK result well correlates with the SM and B-physics, whereas the BNL results are in conflict with the SM with the heavy top quark.

hep-ph↗
arXiv1995

Electromagnetic Catalysis of a Neutrino Radiative decay or One More Source of Information on the Lepton Mixing Angles?

The radiative decay of ultrarelativistic massive neutrino $ν_i \rightarrow ν_j γ$ is investigated in electromagnetic fields in the framework of the Standard Model with lepton mixing. Estimates of the decay probability and ``decay cross-section'' for accelerator neutrinos of high energies in the electric field of nucleus permit one to discuss the general possibility of carrying out the neutrino experiment. Such an experiment could give unique information on mixing angles in the lepton sector of the Standard Model which would be almost independent of the specific neutrino masses.

hep-ph↗
arXiv1995

THREE TYPES OF FERMION MIXING AND POSSIBLE MANIFESTATIONS OF A PATI--SALAM LEPTOQUARK IN THE LOW--ENERGY PROCESSES

I report the recent studies\cite{1,2} on the low--energy manifestations of a minimal extension of the Standard Model based on the quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ of the Pati-Salam type. Given this symmetry the third type of mixing in the interactions ot the $SU(4)_V$ leptoquarks with quarks and leptons is shown to be required. An additional arbitrariness of the mixing parameters could allow, in principle, to decrease noticeably the lower bound on the vector leptoquark mass originated from the low-energy rare processes. The decays $μ\rightarrow e γ$, $μ\rightarrow e γγ$, and $μ\rightarrow e e \bar e$ via the vector leptoquark are analysed and the specific hierarchy of the decay probabilities $Γ(μ\rightarrow e e \bar e) \gg Γ(μ\rightarrow e γγ) \gg Γ(μ\rightarrow e γ)$ is shown to exist. The upper limits on the branching ratios at a level of $10^{-18}$ for the $μ\rightarrow e γγ$ decay and at a level of $10^{-15}$ for the $μ\rightarrow e e \bar e$ decay are established.

hep-ph↗
arXiv1994

Muon decays with lepton--number violation via vector leptoquark

The decays $μ\rightarrow e γ$, $μ\rightarrow e γγ$, and $μ\rightarrow e e \bar e$ are analysed in the framework of the Pati-Salam type quark-lepton symmetry $SU(4)_V \otimes SU(2)_L \otimes G_R$ where the effects of mixing in the quark-lepton currents are taken into account. It is shown that the $μ\rightarrow e γγ$ and $μ\rightarrow e e \bar e$ decays via the vector leptoquark have not a GIM--type suppression, while the $μ\rightarrow e γ$ decay has. So, the specific hierarchy of the decay probabilities could take place $Γ(μ\rightarrow e e \bar e) \gg Γ(μ\rightarrow e γγ) \gg Γ(μ\rightarrow e γ)$. The existing bounds on the vector leptoquark mass and on the mixing matrix elements, based on the data for the $μe$ conversion in nuclei and for the ratio of the $K_{e 2}$ and $K_{μ2}$ decays allow to set the upper limits on the branching ratios at a level of $10^{-18}$ for the $μ\rightarrow e γγ$ decay and at a level of $10^{-15}$ for the $μ\rightarrow e e \bar e$ decay.

hep-ph↗