Tilt-angle dependence of the crystal-assisted pair creation process

Abstract

A theory of enhanced e +−e − pair production for channeled final electron states has recently been advanced with details presented for the case of incident photons perfectly aligned along a crystal axis. We describe here the consequence of lifting the restriction and allowing the incident beam to intersect the axis with a finite angle θ. The predicted rate does not drop off until θ exceeds a critical value θ c (very roughly θ c ≈ 0.02 γ , where γ is the photon energy in units of the electron rest mass energy).