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Abstract

The interaction of an unpolarized electron beam with a counterpropagating
ultraintense linearly polarized laser pulse is investigated in the quantum
radiation-dominated regime. We employ a semiclassical Monte Carlo method to
describe spin-resolved electron dynamics, photon emissions and polarization,
and pair production. Abundant high-energy linearly polarized gamma photons are
generated intermediately during this interaction via nonlinear Compton
scattering, with an average polarization degree of more than 50%, which further
interacting with the laser fields produce electron-positron pairs due to
nonlinear Breit-Wheeler process. The photon polarization is shown to
significantly affect the pair yield by a factor beyond 10%. The considered
signature of the photon polarization in the pair's yield can be experimentally
identified in a prospective two-stage setup. Moreover, the signature can serve
also for the polarimetry of high-energy high-flux gamma photons with a
resolution well below 1% with currently achievable laser facilities.