Orientational dependence of the creation and annihilation of electron–positron pairs in a single-crystal at high energies

Abstract

The process of electron—positron pair annihilation with the creation of a single photon and the opposite process of lepton-pair creation by a high-energy photon without the participation of a third body (in vacuum) are forbidden in accordance with the energy and momentum conservation laws. These processes can occur in materials, but their probability decreases on account of the participation of a third body. However, in oriented single crystals, where relativistic charged particles can exist in states bound to crystal atomic planes or axes (the channeling mode), single-vertex processes (in perturbation theory) can occur. In this paper, the probability of such processes and the threshold conditions for their implementation are estimated.