Neutrinos and electrons in background matter

We present a rather powerful method in investigations of different phenomena that can appear when neutrinos and electrons propagate in background matter. This method is based on the use of the modified Dirac equations for particles wave functions, in which the correspondent effective potentials accounting for the matter influence on particles are included.Comment: submitted to J.Phys.: Conference Series (Proceedings of Neutrino 2006 Conference, June 2006, Santa Fe, New Mexico

Electromagnetic properties of neutrinos: three new phenomena in neutrino spin oscillations

In studies of neutrino electromagnetic properties we discuss three very interesting aspects related to neutrino spin oscillations. First we consider neutrino mixing and oscillations in the mass and flavour bases under the influence of a constant magnetic field with nonzero transversal and longitudinal components. Then we discuss the effect of neutrino spin oscillations induced by electroweak interactions of neutrino with moving matter in case there is matter transversal current or polarization. In the final part of the paper we discuss recently developed approach to description of neutrino spin and spin-flavour oscillations in a constant magnetic field that is based on the use of the exact neutrino stationary states in the magnetic field.Comment: 10 pages, the paper in the proceedings of the 19th International Seminar on High Energy Physics QUARKS-2016 with minor modification

New bounds on neutrino electric millicharge from limits on neutrino magnetic moment

Using the new limit on the neutrino anomalous magnetic moment recently obtained by the GEMMA experiment on measurements of the cross section for the reactor antineutrino scattering on free electrons, we get a new direct upper bound on the neutrino millicharge $\mid q_{\nu} \mid < 1.5 \times 10^{-12} e_0$. This is a factor of 2 more stringent constraint than the previous bound obtained from the TEXONO reactor experiment data that is included to the Review of Particle Properties 2012. We predict that with data from the ongoing new phase of the GEMMA experiment the upper bound on the neutrino millicharge will be reduced to $\mid q_{\nu} \mid < 3.7 \times 10^{-13}e_0$ within two years. We also predict that with the next phase of the considered experiment the upper bound on the millicharge will be reduced by an order of magnitude over the present bound and reach the level $\mid q_{\nu} \mid < 1.8 \times 10^{-13}e_0$ within approximately four years.Comment: 8 pages in LaTex, the approach for accounting the neutrino millicharge contribution to the cross section has been corrected. v3: new references including a reference to Review on Particle Physics by Particle Data Group are added, new more stringent limit on millicharge is predicted for the future release of the GEMMA collaboration result