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

TL;DR

This study investigates how electron/positron spin and photon polarization influence nonlinear Breit-Wheeler pair production in high-power laser interactions, revealing significant polarization effects on particle yields and spectra.

Contribution

It introduces a spin- and polarization-resolved Monte Carlo approach into PIC simulations, highlighting the importance of these effects in 10-PW laser-plasma interactions.

Findings

Gamma photon polarization exceeds 50%

Positron yield decreases by about 10-20% due to polarization effects

High-energy positron spectra show anomalous features related to spin-dependent emissions

Abstract

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 10-PW-class laser pulses with a thin foil target. The processes of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production based on 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 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 class.