COHERENT PAIR PRODUCTION IN CRYSTALS IN PRESENCE OF ACOUSTIC WAVES

摘要

Coherent electron-positron pair production by high-energy photons is investigated in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO_2 single crystal in the case of the deformation field generated by the acoustic wave of the S type. It is shown that, in dependence of the parameters, the presence of deformation can either enhance or reduce the pair creation cross-section.