Konstantin A. Kouzakov

Electromagnetic neutrinos in laboratory experiments and astrophysics

An overview of neutrino electromagnetic properties, which open a door to the new physics beyond the Standard Model, is given. The effects of neutrino electromagnetic interactions both in terrestrial experiments and in astrophysical environments are discussed. The experimental bounds on neutrino electromagnetic characteristics are summarized. Future astrophysical probes of electromagnetic neutrinos are outlined.

Neutrino-impact ionization of atoms in searches for neutrino magnetic moment

The ionization of atomic electrons by scattering of neutrinos is revisited. This process is the one studied in the experimental searches for a neutrino magnetic moment using germanium detectors. Current experiments are sensitive to the ionization energy comparable with the atomic energies, and the effects of the electron binding should be taken into account. We find that the so-called stepping approximation to the neutrino-impact ionization is in fact exact in the semiclassical limit and also that the deviations from this approximation are very small already for the lowest bound Coulomb states. We also consider the effects of electron-electron correlations and argue that the resulting corrections to the ionization of independent electrons are quite small. In particular, we estimate that in germanium these are at a 1% level at the energy transfer down to a fraction of keV. Exact sum rules are also presented as well as analytical results for a few lowest hydrogenlike states.

Magnetic neutrino scattering on atomic electrons revisited

Abstract We reexamine the role of electron binding effects in the inelastic neutrino–atom scattering induced by the neutrino magnetic moment. The differential cross section of the process is presented as a sum of the longitudinal and transverse components, according to whether the force that the neutrino magnetic moment exerts on electrons is parallel or perpendicular to momentum transfer. The atomic electrons are treated nonrelativistically. On this basis, the recent theoretical predictions concerning the magnetic neutrino-impact ionization of atoms are critically discussed. Numerical calculations are performed for ionization of a hydrogenlike Ge +31 ion by neutrino impact.

Agreement of Experiment and Theory on the Single Ionization of Helium by Fast Proton Impact

Even though the study of ion-atom collisions is a mature field of atomic physics, large discrepancies between experiment and theoretical calculations are still common. Here we present experimental results with high momentum resolution on the single ionization of helium induced by 1-MeV protons, and we compare these to theoretical calculations. The overall agreement is strikingly good, and even the first Born approximation yields good agreement between theory and experiment. This has been expected for several decades, but so far has not been accomplished. The influence of projectile coherence effects on the measured data is briefly discussed in terms of an ongoing dispute on the existence of nodal structures in the electron angular emission distributions.

Multiple ionization of C+, N+ and O+ ions by fast electron impact

Absolute cross sections for electron impact single and multiple ionization of C + , N + and O + ions leading to the formation of C q + (q = 2-4), N q + (q = 2-5) and O q + (q = 2-5) are reported. The animated crossed beam method is applied in the energy range extending from the respective thresholds up to 2.5 keV. The concerned target ions belong to the second row of the periodic table, with configurations 2s 2 2p x (x = 1-3). The maximum cross sections for the multiply charged products C q + are found to be in the range from 2.3× 10 -20 cm 2 (for C 4 + ) up to 6.3× 10 -17 cm 2 (for C 2 + ); for N q + they range from 3.0× 10 -22 cm 2 (for N 5 + ) up to 5.1× 10 -17 cm 2 (for N 2 + ) and, lastly, for O q + they range from 5.5× 10 -22 cm 2 (for O 5 + ) up to 5.2× 10 -17 cm 2 (for O 2 + ). The corresponding threshold energies are found to be in satisfactory agreement with spectroscopic values. The general feature of the measured cross sections is investigated. Their values for single ionization are reasonably explained by the calculations using the Coulomb-Born approximation with exchange, while those for multiple ionization are found to agree well with the semiempirical model for q = 3, but they appear to be notably overestimated by a semiempirical Bethe-Born-type formula when q > 3.

Testing neutrino magnetic moment in ionization of atoms by neutrino impact

The atomic ionization processes induced by scattering of neutrinos play key roles in the experimental searches for a neutrino magnetic moment. Current experiments with reactor (anti)neutrinos employ germanium detectors having energy threshold comparable to typical binding energies of atomic electrons, which fact must be taken into account in the interpretation of the data. Our theoretical analysis shows that the so-called stepping approximation to the neutrino-impact ionization is well applicable for the lowest bound Coulomb states, and it becomes exact in the semiclassical limit. Numerical evidence is presented using the Thomas-Fermi model for the germanium atom.

Electromagnetic neutrino-atom collisions: The role of electron binding

We present a new theoretical approach to neutrino-impact atomic excitation and/or ionization due to neutrino magnetic moments. The differential cross section of the process is given by a sum of the longitudinal and transverse terms, which are induced by the corresponding components of the force that the neutrino magnetic moment imposes on electrons with respect to momentum transfer. In this context, the recent theoretical studies devoted to the magnetic neutrino scattering on atoms are critically examined.

Theory of Neutrino-Atom Collisions: The History, Present Status, and BSM Physics

An overview of the current theoretical studies on neutrino-atom scattering processes is presented. The ionization channel of these processes, which is studied in experiments searching for neutrino magnetic moments, is brought into focus. Recent developments in the theory of atomic ionization by impact of reactor antineutrinos are discussed. It is shown that the stepping approximation is well applicable for the data analysis practically down to the ionization threshold.

On neutrino–atom scattering in searches for neutrino magnetic moments

Abstract In the experimental searches for neutrino magnetic moments using germanium detectors one studies the ionization channel in the neutrino-atom scattering. We find that the so-called stepping approximation to the neutrino-impact ionization is exact in the semiclassical limit, and that the deviations from this approximation are very small.

Bound-state β decay of a neutron in a strong magnetic field

The {beta} decay of a neutron into a bound (pe{sup -}) state and an antineutrino in the presence of a strong uniform magnetic field (B > or approx. 10{sup 13} G) is considered. The {beta} decay process is treated within the framework of the standard model of weak interactions. A Bethe-Salpeter formalism is employed for description of the bound (pe{sup -}) system in a strong magnetic field. For the field strengths 10{sup 13} < or approx. B < or approx. 10{sup 18} G the estimate for the ratio of the bound-state decay rate w{sub b} and the usual (continuum-state) decay rate w{sub c} is derived. It is found that in such strong magnetic fields w{sub b}/w{sub c}{approx}0.1-0.4. This is in contrast to the field-free case, where w{sub b}/w{sub c}{approx_equal}4.2x10{sup -6} [J. N. Bahcall, Phys. Rev. 124, 495 (1961); L. L. Nemenov, Sov. J. Nucl. Phys. 15, 582 (1972); X. Song, J. Phys. G: Nucl. Phys. 13, 1023 (1987)]. The dependence of the ratio w{sub b}/w{sub c} on the magnetic field strength B exhibits a logarithmiclike behavior. The obtained results can be important for applications in astrophysics and cosmology.