Incoherent scattering of highly ultrarelativistic channeled particles on electrons

RESUMO

This article systematically examines the effects that must be taken into account when modeling the dechanneling of highly ultrarelativistic charged particles caused by incoherent scattering by electrons of crystal atoms. Changes in the particle electromagnetic field that occur in condensed matter at highly ultrarelativistic energies are taken into account. The excitation of both collectivized electrons and inner-shell electrons of atoms is considered, taking into account thermal vibrations and the inhomogeneous periodic distribution of atoms in crystals. Differences in the calculations of stopping power and mean square scattering angle by electron of channeled particles are described. The need to separate both of them into diffuse processes, accompanied by the transmission of a transverse momentum which does not exceed the transverse momentum of the channeled particles, and instantaneous dechanneling processes with a greater transmitted momentum, the variation range of which reaches several orders of magnitude, is substantiated. The main result of the present work is expressions for the mean square projected scattering angles per unit length in planes parallel and perpendicular to the atomic plane, which also allow for the introduction of effective minimum momenta for incoherent scattering. Expressions of both types take into consideration completely the nonlocal effects of momentum transfer from crystal electrons to particles moving along classical trajectories, and allow for the formulation of simple methods for modeling the incoherent scattering of ultrarelativistic positively charged particles.