具有大角度束流破裂的高能正负电子束碰撞
High-energy electron-positron beam collisions with large-angle disruptions
AI总结：
本研究引入新无量纲参数ε表征高能正负电子碰撞的束流与场动力学，界定ε≳1的大角度破裂极端区域，验证理论模型与全电磁粒子模拟的吻合性，指出传统研究仅适用于ε≪1区域，需用全电磁粒子程序研究极端情形。
AI中文摘要：
我们研究表明，高能正负电子（$e^-e^+$）碰撞中的束流与场动力学可由本研究引入的新无量纲参数$\boldsymbol{\u03b5}$表征。束流破裂效应会使粒子发生横向偏转，偏转角大小与$\boldsymbol{\u03b5}$相当。粒子同时会经历纵向速度的减速（即“制动效应”），减速幅度的标度关系为$\boldsymbol{\u221d \u03b5^2}$。碰撞还会进一步激发纵向电场，其振幅的标度关系为$\boldsymbol{\u221d \u03b5}$。我们将$\boldsymbol{\u03b5 \u2273 1}$（对应大角度束流破裂）界定为一种全新的极端区域，该区域内粒子的横向运动变为强相对论性，制动效应会完全阻止束流传播，甚至使其反向。我们的理论模型与电磁particle-in-cell（粒子网格）模拟结果高度吻合。此前的束流-束流研究（包括传统数值程序）仅适用于$\boldsymbol{\u03b5 \u226a 1}$的区域，无法正确描述该极端区域的束流特征与碰撞亮度，且在$\u03b5$较大时会高估束流-束流效应（包括beamstrahlung（束strahlung）和正负电子对产生），由此证明研究这类区域需要采用全电磁particle-in-cell程序。
英文摘要：
We show that the beam and field dynamics in high-energy electron-positron ($e^-e^+$) collisions are characterized by a new dimensionless parameter introduced as $\varepsilon$ in this study. The disruption effect deflects the particles transversely at angles equal to $\varepsilon$. The particles simultaneously undergo deceleration of longitudinal velocities (a ``braking effect"). The deceleration scales as $\propto \varepsilon^2$. A longitudinal electric field is further provoked, whose amplitude scales as $\propto \varepsilon$. We identify $\varepsilon \gtrsim 1$ (with large-angle disruptions) as a novel extreme regime, where the transverse motion becomes strongly relativistic. The braking effect completely stops and further reverses the beam propagation. Our theoretical model is in excellent agreement with electromagnetic particle-in-cell simulations. The previous beam-beam studies, including legacy numerical codes, apply only to the $\varepsilon \ll 1$ regime. They fail to capture the correct beam features and collision luminosities, and overestimate beam-beam effects (including beamstrahlung and pair production) for considerable $\varepsilon$, thus demonstrating the need for fully electromagnetic particle-in-cell codes to study these regimes.
