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Alexander Studenikin

Publications and source records attributed to Alexander Studenikin.

At least 19 recordsLinked to original sources
arXiv2026

New effect in neutrino spin oscillations in transversal matter currents with nonstandard interactions

We perform a systematic study of a new phenomenon of neutrino spin and spin-flavor oscillations induced by transverse matter currents, based on the developed quantum treatment of the phenomenon. Both standard and nonstandard interactions of neutrinos with the external medium are taken into account. As an example, the oscillations in question are considered under the conditions of a binary neutron star merger model.

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arXiv2026

Quantum field-theoretic framework for neutrino decoherence from scattering in a medium

We develop a theoretical framework for quantum field description of neutrino evolution in a medium, with a focus on quantum decoherence induced by neutrino scattering on fermions. By deriving a generalized Lindblad master equation that accounts for neutrino momentum-changing transitions, we go beyond the standard treatment that assumes fixed neutrino momentum. Our model explicitly connects decoherence parameters to scattering cross sections, offering a bridge between theoretical predictions and experimental constraints on neutrino quantum decoherence. We apply the developed formalism to several scenarios: 1) neutrino scattering on electrons, 2) neutrino scattering on protons and neutrons through non-standard interactions (NSI), 3) neutrino scattering on dark matter fermions. The obtained results demonstrate that decoherence effects can significantly alter neutrino oscillation patterns and provide a new probe for physics beyond the Standard Model.

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arXiv2026

Wave packet description of Majorana neutrino oscillations in a magnetic field

Majorana neutrino oscillations in a magnetic field are considered using the wave packets formalism. The modified Dirac equation for Majorana neutrinos with non-zero transition magnetic moments propagating in a magnetic field is solved analytically in the two flavour case. The expressions for the oscillations probabilities are derived accounting for the decoherence effect emerging at distances exceeding the coherence length. It is shown that for Majorana neutrinos propagating in a magnetic field the coherence length coincides with the coherence length for neutrino oscillations in vacuum when the vacuum frequency is much greater than the magnetic frequency ($ω_{vac} \gg ω_B$), while it is proportional to the cube of the average neutrino momentum if ($ω_{vac} \ll ω_B$). We show that the decoherence effect may appear during neutrino propagation in a magnetic field of supernova.

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arXiv2025

Three-flavour neutrino oscillations in a magnetic field

In this paper we study Dirac and Majorana neutrino oscillations in a magnetic field in the three-flavour case. A theoretical framework developed in \cite{Popov:2019} is extended to the case of three neutrino species, as well as to the Majorana neutrinos case. The closed expression for the Dirac neutrinos flavour and spin oscillations are given. Majorana neutrino oscillations are studied numerically. We show that the probabilities exhibit a complicated interplay of oscillation on magnetic $μ_νB$ and vacuum $Δm^2_{ij}/2p$ frequencies. It is also shown that neutrino oscillations in an interstellar magnetic field can modify neutrino fluxes observed in neutrino telescopes.

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arXiv2025

Neutrino quantum decoherence in a fluctuating ALPs field

The evolution of neutrinos in a fluctuating classical axion-like particles (ALPs) field is investigated. The equation for the neutrino density matrix is obtained in the Redfield form, and the corresponding dissipative matrix is derived. Estimates on the correlation time of the ALPs field fluctuations and on the ALP-neutrino coupling constants are obtained using the limits on the decoherence parameter determined from the analysis of reactor neutrino experiments data.

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arXiv2025

High-energy neutrinos flavour composition as a probe of neutrino magnetic moments

Neutrino propagation in the Galactic and extragalactic magnetic fields is considered. We extend an approach developed in \cite{Popov:2019nkr} to describe neutrino flavour and spin oscillations using wave packets. The evolution equations for the neutrino wave packets in a uniform and non-uniform magnetic fields are derived. The analytical expressions for neutrino flavour and spin oscillations probabilities accounting for damping due to the wave packet separation are obtained for the case of a uniform magnetic field. It is shown that terms in the flavour oscillations probabilities that depend on the magnetic field strength are characterized by two coherence lengths. One of the coherence lengths coincides with the coherence length for neutrino oscillations in vacuum, while the second one is proportional to the cube of the average neutrino momentum $p_0^3$. The probabilities of flavour and spin oscillations are calculated numerically for neutrino interacting with the non-uniform Galactic magnetic field. It is shown that oscillations on certain frequencies are suppressed on the Galactic scale due to the neutrino wave packets separation. The flavour compositions of high-energy neutrino flux coming from the Galactic centre and ultra-high energy neutrinos from an extragalactic sourse are calculated accounting for neutrino interaction with the magnetic field and decoherence due to the wave packet separation. It is shown that for neutrino magnetic moments $\sim 10^{-13} μ_B$ and larger these flavour compositions significantly differ from ones predicted by the vacuum neutrino oscillations scenario.

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arXiv2024

Generalized Lindblad master equation for neutrino evolution

A new theoretical framework, based on the quantum field theory of open systems applied to neutrinos, has been developed. This framework aims to describe the neutrino evolution in external environment, taking into account the effect of neutrino quantum decoherence. We have applied this approach to investigate a novel mechanism for neutrino quantum decoherence, which arises due to the neutrino decay into a lighter neutrino state and a massless particle, as well as the inverse process of absorption of a massless particle by a neutrino. We derived the new generalized Lindblad master equation for the neutrino evolution that accounts for neutrino transitions between states with different momenta. We also demonstrate that studying of neutrino quantum decoherence through this master equation provides a unique possibility to determine or limit the neutrino decay width. On this basis we obtained the constraint on neutrino lifetime $\frac{τ_2}{m_2} > 1.83 \times 10^{-10} \frac{s}{eV}$ (for the case of the Dirac neutrino scalar decay and neutrino degenerate hierarchy).

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arXiv2024

Neutrino Electromagnetic Properties

Neutrinos are neutral in the Standard Model, but they have tiny charge radii generated by radiative corrections. In theories Beyond the Standard Model, neutrinos can also have magnetic and electric moments and small electric charges (millicharges). We review the general theory of neutrino electromagnetic form factors, which reduce, for ultrarelativistic neutrinos and small momentum transfers, to the neutrino charges, effective charge radii, and effective magnetic moments. We discuss the phenomenology of these electromagnetic neutrino properties and we review the existing experimental bounds. We briefly review also the electromagnetic processes of astrophysical neutrinos and the neutrino magnetic moment portal in the presence of sterile neutrinos.

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arXiv2024

Wave packet treatment of neutrino flavour and spin oscillations in galactic and extragalactic magnetic fields

We consider neutrino flavour and spin oscillations in a magnetic field using formalism of wave packets. Decoherence effects due to neutrino wave packets separation are studied. The considered effects are especially important for describing astrophysical neutrino oscillations, since they propagate on kiloparsec scale and bigger. The obtained results are of interest for neutrino telescopes IceCube, Baikal-GVD and KM3NeT, and also can be applied for description of supernovae neutrino oscillations effects would be detected by JUNO and Hyper-Kamiokande.

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arXiv2023

Oscillations of Majorana neutrinos in supernova and CP violation

Leptonic CP violation is one of the most important topics in neutrino physics. CP violation in the neutrino sector is strongly related to the nature of neutrinos: whether they are Dirac or Majorana particles. In \cite{Popov:2021icg} we have shown that for Majorana neutrinos arance of nonzero Majorana CP-violating phases combined with strong magnetic field during supernova core-collaple can induce new resonances in neutrino oscillations, for example in $ν_e \to \barν_τ$ channel. In this contribution we further study new resonances in Majorana neutrino oscillations, in particular energy dependence of amplitudes of these resonances. Our findings suggest a potential astrophysical setup for studying the nature of neutrino masses and leptonic CP violation and may be important for future neutrino experiments, such as JUNO, Hyper-Kamiokande and DUNE.

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arXiv2023

A proposal for experiment with high-intensity tritium neutrino source in Sarov: The search for coherent elastic neutrino-atom scattering and neutrino magnetic moment

A description of the current state of the project for the study of coherent elastic neutrino-atom scattering using a tritium source and liquid helium detector is given. The project was proposed in our paper in 2019 and its main goal is to obtain a new record limit on the neutrino magnetic moment at a level below 10^{-12}μ_B using a tritium antineutrino source with an intensity of 10 MCi or even 40 MCi.

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arXiv2023

Elastic neutrino scattering on nuclear systems as a probe of neutrino electromagnetic interactions

We study the electromagnetic contribution to elastic neutrino-proton and neutrino-neutron scattering processes. The neutrino electromagnetic charge, magnetic, electric, and anapole form factors of both diagonal and transition types in the mass basis are taken into account in the present formalism. When treating the nucleon electromagnetic vertex, we take into account not only the charge and magnetic form factors of a nucleon, but also its electric and anapole form factors. We examine how the effects of the neutrino magnetic moment can be disentangled from those of the strange quark contributions to the nucleon weak neutral current form factors.

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arXiv2023

Neutrino mixing angle and neutrino oscillation in ALPs matter

Axions and axion-like particles (ALPs) are among of the most popular candidates for dark matter. Axions are also considered as new physics contributions to the muon g-2. Following the existed interest to ALPs we consider interaction between neutrinos and hypothetical axion-like particles and derive for the first time the probability of neutrino oscillations accounting for their interactions mediated by ALPs. The corresponding effective mixing angle is derived.

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arXiv2023

Neutrino propagation in moving and polarized matter

The rapid development of neutrino astronomy, which is expressed, among other things, in the emergence of new neutrino mega-projects capable of efficient registering astrophysical neutrino fluxes requires a detailed knowledge of neutrino evolution inside neutrino sources (type II supernovae, gamma-ray bursts). This evolution can be influenced by many factors, each should be accounted for by a relevant theory. In this work, we develop the theory of neutrino propagation in moving and/or polarized matter by introducing for the first time an exact spin integral of motion. This enables us to obtain the neutrino dispersion under these conditions and resolve it for most important cases. Our approach opens up the possibility to consistently classify neutrino states in moving and/or polarized medium and, as a consequence, to give a systematic description of the related physical phenomena (e.g., neutrino oscillations, neutrino electromagnetic radiation).

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arXiv2023

Elastic neutrino-atom scattering as a probe of neutrino millicharge and magnetic moment

Neutrino scattering on atomic systems at low-energy transfer is a powerful tool for searching the neutrino electromagnetic interactions. The regime of coherent elastic neutrino-atom scattering, i.e., when the atom recoils as a pointlike particle, can be effectively fulfilled in the case of tritium antineutrinos. We present theoretical calculations for coherent elastic neutrino-atom scattering processes on such targets as the H, $^2$H, $^3$He, and $^4$He %, and $^{12}$C atoms. We show how the atomic effects and neutrino electromagnetic properties, namely the neutrino millicharge and magnetic moment, may manifest themselves in the atomic-recoil spectra. Our results can be used in planning the experiments on coherent elastic neutrino-atom scattering (in particular, with superfluid He-4).

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arXiv2023

Quantum decoherence of neutrino mass states

We study the interplay of the neutrino quantum decoherence and bipolar collective neutrino oscillations. Using the numerical simulation of the neutrino evolution in a supernova environment we showthe suppression of the bipolar collective neutrino oscillations by the quantum decoherence of the neutrino mass states.

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arXiv2023

Overview of neutrino electromagnetic properties 2022

Continuing the discussion of the problem of electromagnetic properties of neutrinos, in this note we present additional information on this problem and focus on selected issues that have been developed recently, after the publication of our previous brief review on this topic [1].

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