Production of high-energy transversely-polarized electrons and positrons in crystals

It is demonstrated that a novel phenomenon arises on passage of high energy γ-quanta through a crystal at low angles with respect to the crystallographic planes (axes), viz. the production of transversely polarized electrons and positrons by unpolarized γ-quanta. Estimates based on the theory presented in the paper show that the phenomenon may be used to obtain transversly polarized electrons and positrons with a degree of polarization between 50 and 90%. Energies of hundreds and thousands of GeV may be attained if the γ-quanta are incident on the atomic planes, and energies of tens GeV or higher if the quanta are incident on the atomic axes. Concrete calculations are performed for the polarization, number and angular distributions of the positrons produced by 350 GeV γ-quanta falling on a family (110) planes of a 3x10-4 cm tungsten wafer. Some features of the phenomenon in bent crystals are analyzed