Studies on Characteristics of UHE Gamma-ray Air Showers and Its Detection Capability

建立了考虑初级伽马射线与地磁场相互作用的模拟程序，估算了大气顶部次级粒子(伽马射线和电子)的能谱。由这种次级成分(主要是伽马射线)引发的大气中的空气簇射发展，通过根据AIRES空气簇射代码计算的子簇雨的总和进行了重建。LPM效应对簇射发展的贡献从10^lt；19.3 ev开始，随着伽马射线能量的增加，簇射发展变得缓慢且波动较大。因此，伽马射线与地磁场的相互作用截面从10^lt；19.2 ev开始变大，这取决于地磁场强度和一次能量。受地磁场影响的簇射发展较快，主要是由于能量较低的二次分量的聚集。这两种效应的贡献都强烈地依赖于伽马射线的能量及其到达方向，而簇射特征的显著差异可以看作是这些参数的函数。通常，由新提出的实验测量的空气簇射最大值的平均和个别位置将显示质子和伽马射线引发的空气簇射特征的明显差异，并将有可能估计10^&lt；19&gt；eV以上能量区域的伽马射线强度。

Simulation code has been constructed taking into account of an interaction between primary gamma-ray and geomagnetic field, and energy spectra of secondary particles (gamma-rays and electrons) at the top of atmosphere have been estimated. Air shower development in the atmosphere initiated by such secondary component (dominantly gamma-rays) has been reconstructed by a summation of sub-showers calculated from AIRES air shower code. LPM effect starts its contribution to the shower development from 10^<19.3>eV and makes shower development to be slower and larger fluctuation with increasing a gamma-ray energy. Hence, interaction cross-section between gamma-ray and geomagnetic field becomes larger from 10^<19.2>eV depending on the geomagnetic field strength and primary energy. Shower development affected by geomagnetic field becomes faster due to the bunch of secondary component with lower energies. The contributions of both effect strongly depend on gamma-ray energy and its arrival direction, and remarkable differences on the shower characteristics could be seen as a function of these parameters. Typically average and individual positions of air shower maximum measured by proposed newly experiments will show clear differences of air shower characteristics between proton and gamma-ray initiated ones, and it will be possible to estimate gamma-ray intensity in an energy region above 10^<19>eV.