AI 中文总结
本研究开展超强激光与GeV电子束对撞引发的QED级联的代分辨分析，通过追踪级联各代演化的蒙特卡洛模型，发现辐射反应抑制高产额、正电子能谱随参数软化等规律，建立标度关系，提出用可观测参量诊断激光强度与脉宽的新方法。
AI 中文摘要
我们对超强激光脉冲（$a_0 = 200$–$1000$）与$10$ GeV电子束对头碰撞引发的簇射型、依赖自旋与偏振的量子电动力学（QED）级联开展了代分辨分析。借助追踪不同代级联演化的蒙特卡洛模型，我们发现辐射反应会强烈抑制高代粒子的产额。正电子能谱随$a_0$的增大呈现系统性软化，且由于非线性布赖特-惠勒对产生过程中的偏振选择性耗尽效应，平均光子偏振度$\overlineξ_3$随脉宽$τ$增大而升高。我们确定了一个标度关系$a_0^2τ$，该关系同时支配最大级联代数$G_{\max}$与后向发射光子占比$F_r$，由此建立了利用$F_r$和正电子峰能$\varepsilon_+^{\rm peak}$这两个可观测参量诊断激光强度与脉宽的实验可及方法。这些依赖代的特征为强场QED区域内超强激光参数的表征提供了一种潜在的发次分辨、作用后测量的途径。
英文摘要
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 ($a_0 = 200$--$1000$) 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 $a_0$, and the average photon polarization $\overlineξ_3$ increases with pulse duration $τ$ due to polarization-selective depletion in nonlinear Breit--Wheeler pair production. We identify a scaling relation $a_0^2τ$ that governs both the maximum cascade generation $G_{\max}$ and the fraction of backward-emitted photons $F_r$, thereby establishing experimentally accessible diagnostics for laser intensity and pulse duration using two observables: $F_r$ and the positron peak energy $\varepsilon_+^{\rm peak}$. These generation-dependent signatures suggest a potential shot-resolved, post-interaction approach for characterization of ultraintense laser parameters in the strong-field QED regime.
