  We study particle and chirality production from the vacuum in the presence of
a slow strong parallel electromagnetic field superimposed by a fast weak
perturbative electromagnetic field. We derive an analytical formula for the
particle and chirality production number based on the perturbation theory in
the Furry picture. With the formula, we analytically discuss the interplay and
dynamical assistance between the Schwinger mechanism and one-photon pair
production and clarify effects of a parallel slow strong magnetic field. We
also show that the dynamical assistance can significantly enhance chirality
production, and that a sizable amount of chirality can be produced even for
massive particles. Phenomenological applications including heavy-ion collisions
and intense laser experiments are also discussed.
