Influence of polarization on back-reflected e - e + pair jets from laser-electron collision

We investigate the effect of laser polarization on spatial and momentum distribution of back-reflected e- e+ pairs from collisions of an intense laser pulse (I = 5 × 1022 W/cm2 ) with a counter-propagating 5 GeV electron beam. During the pair production significant amount of particles (106 − 107 ) are ejected in the opposite direction of the incoming electron beam (back-reflected), they are trapped by and co-propagate with the laser beam, gaining energy up to a GeV level. From our multi-dimensional particle-in-cell studies, we observe that laser polarization affects the angular distribution of these particles: a linearly polarized pulse produces two transversely separated particle jets, while a circular one leads to the formation of a radially symmetric cone-shaped emission. The results presented here add insights for future experiments performed at multi-PW laser facilities.