Spin polarization of electrons by ultraintense lasers

Abstract

Electrons in plasmas produced by next-generation ultraintense lasers ($I>5\ifmmode\times\else\texttimes\fi{}{10}^{22}\phantom{\rule{0.16em}{0ex}}\mathrm{W}/{\mathrm{cm}}^{2}$) can be spin polarized to a high degree (10%--70%) by the laser pulses on a femtosecond time scale. This is due to electrons undergoing spin-flip transitions as they radiate $\ensuremath{\gamma}$-ray photons, preferentially spin polarizing in one direction. Spin polarization can modify the radiation reaction force on the electrons, which differs by up to 30% for opposite spin polarizations. Consequently, the polarization of the radiated $\ensuremath{\gamma}$-ray photons is also modified: the relative power radiated in the $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ components increases and decreases by up to 30%, respectively, potentially reducing the rate of pair production in the plasma by up to 30%.