2026/08/04 by Ke-Jia Wei, Feng Wan, Hao-Tian Wang +3
Physics and Astronomy · #physics.plasm-ph
arxiv created 2026/08/04 · arxiv updated 2026/08/05
We present a generation-resolved analysis of shower-type, spin- and polarization-dependent quantum electrodynamics (QED) cascades initiated by head-on collisions of ultraintense laser pulses (a0 = 200--1000) with 10~GeV electron bunches. Using a Monte Carlo model that tracks cascade evolution across distinct generations, we shows that radiation reaction strongly suppresses high-generation yields. The positron energy spectrum exhibits a systematic softening with increasing a0, and the average photon polarization ξ3 increases with pulse duration τ due to polarization-selective depletion in nonlinear Breit--Wheeler pair production. We identify a scaling relation a02τ that governs both the maximum cascade generation Gmax and the fraction of backward-emitted photons Fr, thereby establishing experimentally accessible diagnostics for laser intensity and pulse duration using two observables: Fr and the positron peak energy ε+\rm peak. These generation-dependent signatures suggest a potential shot-resolved, post-interaction approach for characterization of ultraintense laser parameters in the strong-field QED regime.