Symmetries in nonlinear Bethe-Heitler process

Nonlinear Bethe-Heitler process in a bichromatic laser field is investigated using strong-field QED formalism. Symmetry properties of angular distributions of created $e^-e^+$ pairs are analyzed. These properties are showed to be governed by a behavior of the vector potential characterizing the laser field, rather than by the respective electric field component.