Spin And Polarization Effects On The Nonlinear Breit-Wheeler Pair Production In Laser-Plasma Interaction

The spin effect of electrons/positrons (e (-)/e (+)) and polarization effect of gamma photons are investigated in the interaction of two counter-propagating linearly polarized laser pulses of peak intensity 8.9 x 10(23) W cm(-2) with a thin foil target. The processes of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production based on the spin- and polarization-resolved probabilities are implemented into the particle-in-cell (PIC) algorithm by Monte Carlo methods. It is found from PIC simulations that the average degree of linear polarization of emitted gamma photons can exceed 50%. This polarization effect leads to a reduced positron yield by about 10%. At some medium positron energies, the reduction can reach 20%. Furthermore, we also observe that the local spin polarization of e (-)/e (+) leads to a slight decrease of the positron yield about 2% and some anomalous phenomena about the positron spectrum and photon polarization at the high-energy range, due to spin-dependent photon emissions. Our results indicate that spin and polarization effects should be considered in calculating the pair production and laser-plasma interaction with the laser power of 10 PW to 100 PW classes.