Electron spin- and photon polarization-resolved probabilities of strong-field QED processes

Abstract

A derivation of fully polarization-resolved probabilities is provided for high-energy photon emission and electron-positron pair production in ultrastrong laser fields. The probabilities resolved in both electron spin and photon polarization of incoming and outgoing particles are indispensable for developing QED Monte Carlo and QED-Particle-in-Cell codes, aimed at the investigation of polarization effects in nonlinear QED processes in ultraintense laser-plasma and laser-electron beam interactions, and other nonlinear QED processes in external ultrastrong fields, which involve multiple elementary processes of a photon emission and pair production. The quantum operator method introduced by Baier and Katkov is employed for the calculation of probabilities within the quasiclassical approach and the local constant field approximation. The probabilities for the ultrarelativistic regime are given in a compact form and are suitable to describe polarization effects in strong laser fields of arbitrary configuration, rendering them very well suited for applications.

Advances in QED with intense background fields

“…The asymptotic scalings of the completely polarised NLC rates for small and large χ were presented in [231]. The rates for polarised photon emission from polarised electrons have been independently derived in the quasiclassical method of Baier, Katkov and Strakhovenko (BKS) [236] in [237,238,239,240]. As far as we can tell the first complete results for all particles polarised were presented just very recently in Ref.…”

“…The pair production rates from the quasiclassical method of Baier, Katkov and Strakhovenko (BKS) [236], with all particles polarised were given in Ref. [277,240]. For an infinite monochromatic plane wave the completely spin-and polarisation dependent cross sections had been obtained already in [278] (cf.…”

Production of polarized particle beams via ultraintense laser pulses

“…However, the situation is different for a high-energy (multi-GeV) incoming electron (χ e ∼ 1): the probability of spin-flip is larger than that of spin-nonflip after radiation. In this case, the spin and polarization modify the Compton scattering and its concomitant radiation-reaction effects, rather significantly [45,67,68,74,[113][114][115]. The polarization of a high-energy electron in strongly NLC scattering is similar to ST polarization: a TSP electron (positron) beam will be formed spontaneously due to the electron (positron) spin transition to the reverse (same) direction, respectively, as that of the static magnetic field under the influence of synchrotron radiation.…”

“…In addition to the above mentioned spin-flip mechanism, in the strongly NLC regime, another polarization process of electrons can be induced by the spin-dependent radiation-reaction, which has been clarified by means of QO approach [74]. Summing over the final electron spins and photon polarizations, the radiation probability of NLC scattering, depending on the initial spins, is given by [45]…”

“…In this regime, the dynamics of particles can be considered to be quasiclassical. The polarized NLC and NBW processes are extensively investigated employing the QO approach in the LCFA regime [51,52,54,74] and in the weakly nonlinear regime [75,76]. It has the advantage of allowing for numerical solutions in arbitrary electromagnetic fields, which is favored in the investigation of interactions between ultraintense tightly-focused laser pulses and ultrarelativistic electron beams.…”