Implementing nonlinear Compton scattering beyond the local-constant-field approximation
Implementing nonlinear Compton scattering beyond the local-constant-field approximation
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DOI：
10.1103/physreva.98.012134
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发表时间：
2017-08
影响因子：
2.9
通讯作者：
A. Piazza;M. Tamburini;S. Meuren;S. Meuren;C. Keitel
中科院分区：
文献类型：
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作者：
A. Piazza;M. Tamburini;S. Meuren;S. Meuren;C. Keitel
在计算背景经典场中物理过程发生的概率时，局部常场近似（LCFA）依赖于忽略过程形成区域内外场的时空变化的可能性。这种近似被广泛应用于强场QED中，因为它允许人们从恒定电磁场中计算的相应量开始评估在任意电磁场中发生的过程的概率。在这里，我们仔细研究了非线性康普顿散射情况下LCFA的有效性，重点关注发射光子的能量对该过程形成长度的作用。特别地，我们解析地导出了每单位光子光锥能量${k}_{\ensuremath{-}}$的发射概率的渐近行为，并证明它在${k}_{\ensuremath{-}}\ensuremath{\rightarrow}0$时趋向于一个常数。由于数值编码是解释当前和即将进行的强场QED实验的重要工具，我们得到了光子发射概率的改进近似，并在数值上实现了它，并表明它修正了LCFA在红外区域的不准确行为，使得它在定性和定量上也与红外区域的全强场QED概率一致。
In the calculation of probabilities of physical processes occurring in a background classical field, the local-constant-field approximation (LCFA) relies on the possibility of neglecting the space-time variation of the external field within the region of formation of the process. This approximation is widely employed in strong-field QED as it allows one to evaluate probabilities of processes occurring in arbitrary electromagnetic fields starting from the corresponding quantities computed in a constant electromagnetic field. Here, we scrutinize the validity of the LCFA in the case of nonlinear Compton scattering focusing on the role played by the energy of the emitted photon on the formation length of this process. In particular, we derive analytically the asymptotic behavior of the emission probability per unit of photon light-cone energy ${k}_{\ensuremath{-}}$ and show that it tends to a constant for ${k}_{\ensuremath{-}}\ensuremath{\rightarrow}0$. With numerical codes being an essential tool for the interpretation of present and upcoming experiments in strong-field QED, we obtained an improved approximation for the photon emission probability, implemented it numerically, and showed that it amends the inaccurate behavior of the LCFA in the infrared region, such that it is in qualitative and good quantitative agreement with the full strong-field QED probability also in the infrared region.