Multi-photon regime of non-linear Breit-Wheeler and Compton processes in short linearly and circularly polarized laser pulses

Non-linear Breit-Wheeler e+e− pair production and its crossing channel - the non-linear Compton process - in the multi-photon regime are analyzed for linearly and circularly polarized short laser pulses. We show that (i) the azimuthal angular distributions of outgoing electrons in these processes differ on a qualitative level, and (ii) they depend on the polarization properties of the pulses. A finite carrier envelope phase (CEP) leads to a non-trivial non-monotonic behavior ofthe azimuthal angle distributions of the considered processes. That effect can be used for the (CEP) determination.