  This work aims to study theoretically the electron-proton scattering for
initially spin-polarized electrons in the presence of a circularly polarized
electromagnetic field. Using the first Born approximation and the Dirac-Volkov
states for dressed electrons, we derive an analytic expression for the
differential cross-section with the help of the spin-helicity formalism.
Meanwhile, a well-known concept of spin-flip and spin non-flip differential
cross sections is applied. The influence of the electromagnetic field on the
degree of polarization of the scattered electron is investigated, and the
effect of electron spin polarization is examined. We found that the initial
spin of the electron can be affected depending on its kinetic energy during the
scattering process. This work is a continuation of a recent paper in which we
studied the unpolarized electron-proton scattering in the presence of a laser
field (Dahiri, et al., Laser Phys. Lett. 18 (2021) 096001).
