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Abstract

Impacts of spin-polarization of an ultrarelativistic electron beam head-on
colliding with a strong laser pulse on emitted photon spectra and electron
dynamics have been investigated in the quantum radiation regime. We simulate
photon emissions quantum mechanically and electron dynamics semiclassically via
taking spin-resolved radiation probabilities in the local constant field
approximation. A small ellipticity of the laser field brings about an asymmetry
in angle-resolved photon spectrum, which sensitively relies on the polarization
of the electron beam. The asymmetry is particularly significant in high-energy
photon spectra, and is employed for the polarization detection of a high-energy
electron beam with extraordinary precision, e.g., better than 0.3\% for a
few-GeV electron beam at a density of the scale of $10^{16}$ cm$^{-3}$ with
currently available strong laser fields. This method demonstrates for the first
time a way of single-shot determination of polarization for ultrarelativistic
electron beams via nonlinear Compton scattering. A similar method based on the
asymmetry in the electron momentum distribution after the interaction due to
spin-dependent radiation reaction is proposed as well.