Abstract
We study oscillations of Dirac neutrinos in background matter and a plane electromagnetic wave. First, we find the new exact solution of the Dirac-Pauli equation for a massive neutrino with the anomalous magnetic moment electroweakly interacting with matter under the influence of a plane electromagnetic wave with the circular polarization. We use this result to describe neutrino spin oscillations in the external fields in question. Then we consider several neutrino flavors and study neutrino spin-flavor oscillations in this system. For this purpose we formulate the initial condition problem and solve it accounting for the considered external fields. We derive the analytical expressions for the transition probabilities of spin-flavor oscillations for different types of neutrino magnetic moments. These analytical expressions are compared with the numerical solutions of the effective Schr\"odinger equation and with the findings of other authors. In particular, we reveal that a resonance in neutrino spin-flavor oscillations in the considered external fields cannot happen contrary to the previous claims. Finally, we briefly discuss some possible astrophysical applications.
Highlights
Nowadays it is commonly believed that neutrinos possess nonzero masses and mixing between different flavor eigenstates [1]
This kind of interaction, it is quite weak, can significantly influence the process of neutrino flavor oscillations resulting in the resonance enhancement of the transition probability, known as the Mikheyev-Smirnov-Wolfenstein (MSW) effect [3]
Neutrino spin and spin-flavor oscillations in matter and an electromagnetic wave were previously discussed in Refs. [11,12] Recently, we demonstrated in Ref. [13] that the results of Ref. [11] are not applicable for the description of spin-flavor oscillations
Summary
Nowadays it is commonly believed that neutrinos possess nonzero masses and mixing between different flavor eigenstates [1]. As constituents of the standard model, neutrinos can interact with other fermions, which a background matter is made of, by exchanging virtual W and Z bosons This kind of interaction, it is quite weak, can significantly influence the process of neutrino flavor oscillations resulting in the resonance enhancement of the transition probability, known as the Mikheyev-Smirnov-Wolfenstein (MSW) effect [3]. Neutrino magnetic moments result in the particle spin precession in an external electromagnetic field. There is a possibility for neutrinos to change both flavor and the polarization in an external electromagnetic field In this situation, these transitions are named neutrino spin-flavor oscillations. Neutrino spin and spin-flavor oscillations in matter and an electromagnetic wave were previously discussed in Refs.
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