Photon-polarization-resolved linear Breit-Wheeler pair production in a laser-plasma system

Abstract: The linear Breit-Wheeler (LBW) process, mediated by photon-photon collisions, can emerge as the dominant pair production mechanism in the ultraintense laser-plasma interaction for laser intensities below $10^{23}~\rm W/cm^2$. Here, we explore the role of photon polarization in LBW pair production for a 10 PW-class, linearly polarized laser interacting with a solid-density plasma. The motivation for this investigation lies in two main aspects: photons emitted via nonlinear Compton scattering are inherently linearly polarized, and the LBW process exhibits a distinct sensitivity to photon polarization. By leveraging particle-in-cell simulations that self-consistently incorporate photon-polarization-resolved LBW pair production, our results reveal that photon polarization leads to a 5\% to 10\% reduction in the total LBW positron yield. This suppression arises because the polarization directions of the colliding photons are primarily parallel to each other, resulting in a diminished LBW cross section compared to the unpolarized case. The influence of photon polarization weakens as the laser intensity increases.