arXiv subjects
Publications and source records attributed to Alexander Studenikin.
We briefly review the matter effects in case of Dirac and Majorana neutrino propagation in medium. We develop the quantum treatment of neutrinos in matter: using the generalized Dirac equations for Dirac and Majorana neutrinos wave functions in matter we get the explicit expressions for the corresponding Green functions.
We develop the quantum theory of the spin light of neutrino ($SLν$) exactly accounting for the effect of background matter. Contrary to the already performed studies of the $SLν$, in this paper we derive explicit and closed expressions for the $SLν$ rate and power and for the emitted photon energy, which are valid for an arbitrary matter density (including very high values). The spatial distribution of the radiation power and the dependence of the emitted photon energy on the direction of radiation are also studied in detail for the first time. We analyze the $SLν$ polarization properties and show that within a wide range of neutrino momenta and matter densities the $SLν$ radiation is circularly polarized. Conditions for effective $SLν$ photon propagation in the electron plasma are discussed. It is also shown that in dense matter the average energy of the emitted photon can reach values in the range from one third of the neutrino momentum up to one half of the neutrino energy in matter. The main features of the studied radiation are summarized, and possibilities for the $SLν$ production during different astrophysical and cosmology processes are discussed.
We consider propagation of a massive neutrino in matter within the quantum approach based on the two equations for the neutrino field: the first one is the Dirac-Pauli equation for a massive neutrino in an external magnetic field generalized on the inclusion of effects of the background matter; the second one is the modified Dirac equation derived directly from the neutrino-matter interaction Lagrangian. On the basis of these two equations the quantum theory of a neutrino moving in the background matter is developed (the exact solutions of these equations are found and classified over the neutrino spin states, the corresponding energy spectra are also derived). Using these solutions we study within the quantum approach the spin light of neutrino ($SLν$) in matter with the effect of a longitudinal magnetic field being also incorporated. In particular, the $SLν$ radiation rate and total power are derived. The use of the generalized Dirac-Pauli equation also enables us to consider the $SLν$ in matter polarized under the influence of strong magnetic field.
On the basis of the exact solutions of the modified Dirac equation for a massive neutrino moving in matter we develop the quantum theory of the spin light of neutrino ($SLν$). The expression for the emitted photon energy is derived as a function of the density of matter for different matter compositions. The dependence of the photon energy on the helicities of the initial and final neutrino states is shown explicitly. The rate and radiation power of the $SLν$ in matter are obtained with the emitted photon linear and circular polarizations being accounted for. The developed quantum approach to the $SLν$ in matter (which is similar to the Furry representation of electrodynamics) can be used in the studies of other processes with neutrinos in the presence of matter
Electromagnetic form factors of a massive neutrino are studied in a minimally extended standard model in an arbitrary $R_ξ$ gauge and taking into account the dependence on the masses of all interacting particles. The contribution from all Feynman diagrams to the charge, magnetic, and anapole form factors, in which the dependence on the masses of all particles as well as on gauge parameters is accounted for exactly, are obtained for the first time in explicit form. The asymptotic behavior of the magnetic form factor for large negative squares of the momentum of an external photon is analyzed and expression for the anapole moment of a massive neutrino is derived. The results are generalized to the case of mixing between various generations of the neutrino. Explicit expressions are obtained for the charge, magnetic, and electric dipole and anapole transition form factors as well as for the transition electric dipole moment.
Starting with the Dirac-Pauli equation for a massive neutrino in an external magnetic field, we propose a new quantum equation for a neutrino in the presence of the background matter. On this basis the quantum theory of a neutrino moving in the background matter is developed: i) for the particular case of the matter with a constant density the exact solutions of this new equation are found and classified over the neutrino spin states, ii) the corresponding energy spectrum is also derived accounting for the neutrino helicity. Using these solutions we develop the quantum theory of the spin light of neutrino ($SLν$) in the matter. The $SLν$ radiation rate and total power are derived for different linear and circular polarizations of the emitted photons. Within the solid base of the developed quantum approach, the existence of the neutrino self-polarization effect in the matter is also shown.
We propose a modified Dirac equation for a massive neutrino moving in the presence of the background matter. The effects of the charged and neutral-current interactions with the matter as well as the matter motion and polarization are accounted for. In the particular case of the matter with a constant density the exact solutions of this equation are found, the neutrino energy spectrum in the matter is also determined. On this basis the effects of the neutrino trapping and reflection, the neutrino-antineutrino pair annihilation and creation in a medium are studied. The quantum theory of the spin light of neutrino in matter ($SLν$) is also developed.
The quasi-classical theory of the spin light of neutrino ($SLν$) in background matter, accounting for the neutrino polarization, is developed. The neutrino transitions $ν_{L}\to ν_{R}$ and $ν_{R}\to ν_{L}$ rates in matter are calculated. It is shown that the $SLν$ in matter leads to the neutrino conversion from active $ν_{L}$ to sterile $ν_{R}$ states (neutrino self-polarization effect in matter).
In this paper I should like to present {\bf {the four new effects}} in neutrino oscillations that have been recently investigated in my research group at the Department of Theoretical Physics of the Moscow State University. Due to the fact that these studies were stimulated by our previous research of neutrino interactions in the presence of magnetic fields, and also because the year 2004 commemorates the 40th years jubilee since the the first paper on the neutrino interaction in a magnetic field was published, a short review on the first papers dedicated to the problem of neutrinos in magnetic fields, and also on the recent results in this field, prefaces (Section 1) the discussion on {\bf the new effects} in neutrino oscillations. Section 2 is devoted to our recent studies of the electromagnetic properties of a {\it massive} neutrino, including the neutrino magnetic moment for different values of neutrino mass. In Section 3 we discuss {\it \bf the four new effects} in neutrino spin and flavour oscillations in different background environments.
We predict a new mechanism for the spin light of neutrino ($SLν$) that can be emitted by a neutrino moving in gravitational fields. This effect is studied on the basis of the quasiclassical equation for the neutrino spin evolution in a gravitational field. It is shown that the gravitational field of a rotating object, in the weak-field limit, can be considered as an axial vector external field which induces the neutrino spin procession. The corresponding probability of the neutrino spin oscillations in the gravitational field has been derived for the first time. The considered in this paper $SLν$ can be produced in the neutrino spin-flip transitions in gravitational fields. It is shown that the total power of this radiation is proportional to the neutrino gamma factor to the fourth power, and the emitted photon energy, for the case of an ultra relativistic neutrino, could span up to gamma-rays. We investigate the $SLν$ caused by both gravitational and electromagnetic fields, also accounting for effects of arbitrary moving and polarized matter, in various astrophysical environments. In particular, we discuss the $SLν$ emitted by a neutrino moving in the vicinity of a rotating neutron star, black hole surrounded by dense matter, as well as by a neutrino propagating in the relativistic jet from a quasar.
We consider a massive Dirac neutrino electric charge and magnetic moment within the context of the standard model supplied with SU(2)-singlet right-handed neutrino in arbitrary R_ξgauge. Using the dimensional-regularization scheme we start with calculations of the one-loop contributions to the neutrino electromagnetic vertex function exactly accounting for the neutrino and other particles masses. We examine the decomposition of the massive neutrino electromagnetic vertex function and show that it contains only the four form factors. Then we get the closed integral expressions for different contributions to the neutrino electric charge and magnetic form factors. These calculations enable us to follow the neutrino and corresponding charged lepton masses and gauge-fixing parameters dependence. For several one-loop contributions to the neutrino charge and magnetic moment, that were calculated previously by the other authors with mistakes, we find the correct results. We show that the neutrino charge for massive neutrino is a gauge independent and vanishing value in the first two orders of the expansion over the neutrino mass parameter b. In the particular choice of the 't Hooft-Feynman gauge we also demonstrate that the neutrino charge is zero for arbitrary mass of neutrino. For each of the diagrams contributing to the neutrino magnetic moment, we get expressions accounting for the leading and next-to-leading order in b with the gauge dependence shown explicitly. Each of the contributions are finite and the sum of all contributions turns out to be gauge-independent. Our calculations also enable us to get the magnetic moment of a heavy neutrino.
We claim that the neutrino mass squared term cannot appear in the expansion of the neutrino electric charge over the neutrino mass parameter at the one-loop level of the standard model supplied with $\mathrm{SU}(2)$-singlet right-handed neutrino.
Within the recently developed Lorentz invariant approach to neutrino spin and flavour oscillations the following four new effects are discussed: 1) neutrino spin oscillations in different electromagnetic field configurations, 2) neutrino spin precession and oscillations stimulated by weak interaction with background matter without presence of electromagnetic fields, 3) the significant shift of neutrino spin and flavour oscillation resonances by matter moving with relativistic speed, if compared with the case of non-moving matter, 4) the new mechanism of electromagnetic radiation by neutrino moving in background matter and/or electromagnetic fields.
A review of the theoretical and experimental values for the charged lepton (electron and muon) anomalous magnetic moment $a_l= (g_l-2)/2$ is presented. Employing the most accurate value for the fine structure constant $α^{-1}= 137.03599993(52) (0.0038 ppm)$ obtained \cite {Kin196} from the electron $(g-2)$ we find the new complete standard model prediction for the anomalous magnetic moment of the muon $a^{th}_μ= 116591595(67)\times 10^{-11}$. The comparison of this theoretical value and the precise experimental result \cite {Sch} yields the estimation for the difference $Δa_μ= a^{exp}_μ- a^{th}_μ$ at the 95% confidence level: $-95 \times 10^{-10} \leq Δa_μ\leq 236 \times 10^{-10}$. The implication of the expected a factor of about 20 increase of accuracy in the forthcoming Brookhaven National Laboratory measurement of $a_μ$ implies $-47 \times 10^{-11} \leq Δa_μ\leq 118 \times 10^{-11}$, ($95 % C.L.$). This interval is used to get constraints on the "new physics". The value of the one-loop contributions $a^{B_i}_l$ of different bosons predicted within extension of the standard model and coupled to a charged lepton are discussed. The dependence of $a^{B_i}_l$ on the masses of the bosons and leptons of the vacuum polarization loops are investigated. The constraints on "new physics" by requiring that the new contributions $a^{B_i}_μ$ to the muon anomalous magnetic moment lie within the latter interval $Δa_μ$ are obtained.