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L. A. Vassilevskaya

Publications and source records attributed to L. A. Vassilevskaya.

30 records · Page 2Linked to original sources
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↗
arXiv1994

One More Source of Information on the Lepton Mixing Angles

In the framework of the Standard Model with lepton mixing the radiative decay $ν_i \rightarrow ν_j γ$ of a neutrino of high ($E_ν\sim 100 \, GeV$) and super-high ($E_ν\ge 1 \, TeV$) energy is investigated in the Coulomb field of a nucleus. Estimates of the decay probability and ``decay cross-section'' for neutrinos of these energies in the electric field of nucleus permit one to discuss the general possibility of carrying out the neutrino experiment, subject to the condition of availability in the future of a beam of neutrinos of that high energies. Such an experiment could give unique information on mixing angles in the lepton sector of the Standard Model which would be independent of the specific neutrino masses if only the threshold factor ($1 - m_j^4 / m_i^4$) was not close to zero.

hep-ph↗
arXiv1994

The Electromagnetic Catalysis of the Neutrino Radiative Decay

The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ( m_i > m_j )$ in the external electromagnetic field is analyzed in detail in the framework of the standard model with lepton mixing. It is shown, that a sort of a catalysis of the neutrino radiative decay takes place. The effect of catalysis is significant in the strong electromagnetic fields ($F \gg B_e = m^2_e / e \simeq 4.41 \cdot 10^{13}$ G) ; it is more pronounced in the case of the decay of the ultrarelativistic neutrino $(E_ν \gg m_ν)$, even in a relatively weak electromagnetic field ($F \ll m^2_e/e$).

hep-ph↗
arXiv1994

The radiative decay of a high energy neutrino in the Coulomb field of a nucleus

In the framework of the Standard Model with lepton mixing the radiative decay $ν_i \rightarrow ν_j γ$ of a neutrino of high ($E_ν\sim 100 \, GeV$) and super-high ($E_ν\ge 1 \, TeV$) energy is investigated in the Coulomb field of a nucleus. Estimates of the decay probability and ``decay cross-section'' for neutrinos of these energies in the electric field of a nucleus permit one to discuss the general possibility of carrying out a neutrino experiment, subject to the condition of availability in the future of a beam of neutrinos of these high energies. Such an experiment could give unique information on mixing angles in the lepton sector of the Standard Model which would be independent of the specific neutrino masses if only the threshold factor ($1 - m_j^4 / m_i^4$) was not close to zero. (Published in Phys.Lett.B 323 (1994) 179).

hep-ph↗
arXiv1994

Electromagnetic catalysis of the radiative transitions of $ν_i \rightarrow ν_j γ$ type in the field of an intense monochromatic wave

The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ in a circularly polarized electromagnetic wave is investigated within the Standard theory with lepton mixing. The decay probability in the wave field does not contain a threshold factor $\sim ( 1 - m_i / m_j )$ as opposed to the decay probability in a vacuum or in a constant uniform external field. The phenomenon of the gigantic enhancement ( $\sim 10^{33}$ ) of the neutrino decay probability in external wave field is discovered. The probability of the photon splitting into the neutrino pair is obtained. (Published in Phys.Lett.B 321 (1994) 108).

hep-ph↗