发表机构
Institute of Frontier and Interdisciplinary Science, Shandong University（山东大学前沿交叉科学研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过CORSIKA模拟揭示宇宙射线空气簇射中首次相互作用产生的二次谐波各向异性在纵向演化中快速衰减，坐标空间残余微弱但可解析，动量空间在300 g cm$^{-2}$后不可区分。
AI 中文摘要
利用CORSIKA模拟研究了广延空气簇射中继承自首次相互作用的二次谐波各向异性的纵向演化。选取了具有较大初始各向异性的事件。分别使用坐标和动量方位角在多个大气深度处评估二次谐波观测量，并将其与相应的初始谐波方向进行比较。在簇射发展的前20 g cm$^{-2}$内，超过84%的初始二次谐波信号被衰减。在坐标空间中，二次谐波与初始方向的相关性持续到地面水平，其幅度约为初始值的0.09%。该残余量针对匹配的源各向同性参考进行了评估，该参考是通过独立随机化每个选定事件的首次相互作用末态粒子的方位角并在相同大气条件下模拟簇射而构建的。地面水平上坐标空间系综平均差在统计上得到解析，两个样本在事件级分离上几乎没有差异。在动量空间中，在200 g cm$^{-2}$处仍存在弱的系综级残余，而原始信号和源各向同性信号在300 g cm$^{-2}$处变得在统计上不可区分，并在地面水平保持这种状态。
英文摘要
The longitudinal evolution of second-harmonic anisotropy inherited from the first interaction in extensive air showers is investigated with CORSIKA simulations. Events with large initial anisotropy are selected. Second-harmonic observables are evaluated separately using the coordinate and momentum azimuths at several atmospheric depths and compared with their corresponding initial harmonic orientations. More than 84% of the initial second-harmonic signal is attenuated within the first 20 g cm$^{-2}$ of shower development. In coordinate space, the second-harmonic correlation with the initial orientation persists to ground level at approximately 0.09% of its initial magnitude. This residual is evaluated against a matched source-isotropized reference, constructed for each selected event by independently randomizing the azimuths of the first-interaction final-state particles and simulating the shower under identical atmospheric conditions. The positive coordinate-space ensemble-mean difference at ground level is statistically resolved, and the two samples show little event-level separation. In momentum space, a weak ensemble-level residual remains at 200 g cm$^{-2}$, and the original and source-isotropized signals become statistically indistinguishable by 300 g cm$^{-2}$ and remain so at ground level.
Comments20 pages, 5 main figures, 2 appendix figures, and 3 tables
