Spin and polarization effects on the nonlinear Breit–Wheeler pair production in laser-plasma interaction

Abstract

The spin effect of electrons/positrons ( e ^− / e ^+ ) and polarization effect of γ photons are investigated in the interaction of two counter-propagating linearly polarized laser pulses of peak intensity 8.9 × 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 γ 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.

Keywords

• spin and polarization effects
• pair production
• strong-field QED
• laser-plasma interaction
• particle-in-cell simulation