Abstract A method to derive the convenient representations for many two-photon amplitudes is suggested. It is based on the use of the gauge in which the photon propagator has only space components. The amplitudes obtained have no any strong numerical cancellations and, therefore, are very convenient for numerical evaluations. Our approach is illustrated by the consideration of the processes e + e − → e + e − e + e − , e + e − → e + e − μ + μ − , and e + e − → μ + μ − π + π − . The method is extended on the case of polarized particles. The amplitudes obtained in this approach have been employed for extension of the event generator developed by F.A. Berends, P.H. Daverveldt, and R. Kleiss. It allows for simulation of e + e − → 4 l and e + e − → 2 l 2 π processes with π + π − pair in the 1 − − state with accounting for contributions of narrow vector resonances and ISR corrections. The calculations with arbitrary polarization of initial particles is also foreseen.

中文翻译：

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双光子过程的幅度和BDK发生器的扩展

摘要 提出了一种推导出许多双光子振幅的方便表示的方法。它基于使用规范，其中光子传播器只有空间分量。获得的振幅没有任何强烈的数值抵消，因此非常便于数值评估。我们的方法通过考虑过程 e + e − → e + e − e + e − 、e + e − → e + e − μ + μ − 和 e + e − → μ + μ − π + 来说明π - 。该方法扩展到极化粒子的情况。在这种方法中获得的幅度已被用于扩展由 FA Berends、PH Daverveldt 和 R. Kleiss 开发的事件发生器。它允许模拟 e + e - → 4 l 和 e + e - → 2 l 2 π 过程，其中 π + π - 对处于 1 - - 状态，并考虑了窄矢量共振和 ISR 校正的贡献。还可以预见初始粒子的任意极化的计算。