V.N. Baier

Mechanism of electron-positron pair production by high-energy photons in a single crystal

Abstract A mechanism of pair production by photons in an electric field of the axes (planes) of a single crystal is discussed. Simple expressions for the process probability and spectral distribution at κ ≲1 are presented. An analysis of conditions to observe the effect is made.

Quantum effects in radiation emitted by ultrahigh energy electrons in aligned crystals

Abstract The energy losses and the radiation spectra of electrons moving in the field of the single crystals axes have been calculated in the energy range where the radiation in an external field becomes essentially quantum. Comparison with the experimental data has been made.

Pair creation by a photon in an electric field

Abstract The process of pair creation by a photon in a constant and homogeneous electric field is investigated basing on the polarization operator in the field. The total probability of the process is found in a relatively simple form. At high energy the quasiclassical approximation is valid. The corrections to the standard quasiclassical approximation (SQA) are calculated. In the region of relatively low photon energies, where SQA is unapplicable, the new approximation is used. It is shown that in this energy interval the probability of pair creation by a photon in electric field exceeds essentially the corresponding probability in a magnetic field. This approach is valid at the photon energy much larger than the “vacuum” energy in electric field: ω ≫ e E / m . For smaller photon energies the low energy approximation is developed. At ω ≪ e E / m the found probability describes the absorption of soft photon by the particles created by an electric field.

Radiation in oriented single crystals: Status of theory and experiment

Abstract It is shown that the peak in the energy loss distribution, observed by Belkacem et al., can be described in the frame of an approach developed by the authors. This means that the whole set of experimental data agrees quite satisfactorily with the theory.

On the radiation theory of high energy electrons in aligned single crystals

Abstract A general approach is developed for a description of the radiation emitted by high energy particles in aligned single crystals. At small angles of incidence, this theory describes the radiation in the field of separate axes and, at large angles of incidence, goes over to the coherent bremsstrahlung theory.

Electron-positron pair creation by photons in an aligned single crystal: comparison of theory with experiment

Abstract The creation of electron-positron pairs by 50–110 GeV photons directed along the 〈110〉 axis of a cooled crystal is considered. The results obtained are compared with a very recent experiment performed in CERN. Radiation from electrons is also discussed.

Coherent and incoherent radiation from high-energy electron and the LPM effect in oriented single crystal

The process of radiation from high-energy electron in oriented single crystal is considered using the method which permits inseparable consideration of both coherent and incoherent mechanisms of photon emission. The total intensity of radiation is calculated. The theory, where the energy loss of projectile has to be taken into account, agrees quite satisfactory with available CERN data. It is shown that the influence of multiple scattering on radiation process is suppressed due to action of crystal field.

Coherent and incoherent pair creation by a photon in oriented single crystal

Abstract The new approach is developed for study of electron–positron pair production by a photon in oriented single crystal. It permits indivisible consideration of both coherent and incoherent mechanisms of pair creation and includes the action of field of axis (or plane) as well as the multiple scattering of particles of the created pair (the Landau–Pomeranchuk–Migdal (LPM) effect). From obtained integral probability of pair creation, it follows that multiple scattering appears only for relatively low energy of photon, while at higher photon energy the field action excludes the LPM effect. The found probabilities agree quite satisfactory with recent CERN experiment.

Anomalous magnetic moment of the electron in a medium

Abstract Radiative effects are considered for an electron moving in a medium in the presence of an external electromagnetic field. Anomalous magnetic moment (AMM) of the electron in α -order is calculated under these conditions in the form of two-dimensional integral. Behavior of AMM of high energy electron under influence of multiple scattering in a medium is analyzed. Both mentioned effects lead to reduction of AMM.Radiative effects are considered for an electron moving in a medium in the presence of an external electromagnetic field. Anomalous magnetic moment (AMM) of the electron in alpha-order is calculated under these conditions in the form of two-dimensional integral. Behavior of AMM of high energy electron under influence of multiple scattering in a medium is analyzed. Both mentioned effects lead to reduction of AMM.

QUANTUM THEORY OF TRANSITION RADIATION AND TRANSITION PAIR CREATION

Abstract A theory of the transition radiation and the transition pair creation is developed in the frame of QED. The spectral-angular distributions of probability of the transition radiation and of the transition pair creation are found. The total energy losses of an electron and the total probability of pair creation by a photon are calculated and analyzed. Features of radiation and pair creation processes in a superdense medium (typical for white dwarfs) are discussed.