标题： 最高能量宇宙射线的质量组成研究 显示英文标题

标题： Mass Composition Studies of the Highest Energy Cosmic Rays

摘要： 最高能宇宙射线的质量组成测定是宇宙射线实验中最大的挑战之一。 由于通量非常低，最高能宇宙射线只能间接观测到。 利用大气作为大型靶标，空气荧光探测器能够追踪广延大气簇射在大气中的大小演化（即簇射纵向剖面）。 目前，分析所检测到的纵向剖面特征是提取关于初级宇宙射线质量组成信息的最可靠方法。 在这篇进展报告中，我将详细描述皮埃尔-奥格延长率研究，并展示使用表面和荧光探测器的信息进行质量组成研究的潜力，将其作为一个整体分析的一部分。 就质量组成而言，当前数据的解释很大程度上依赖于高能强子相互作用模型。 使用标准强子相互作用模型，数据显示出组成变得较轻，直到大约2 $\times$ 10$^{18}$ $eV$ ，超过该值后又变得更重。 这种在2 $\times$ 10$^{18}$ $eV$ 处质量组成的明显变化似乎与观测到的能量谱指数变化相关联。 显示英文摘要

摘要： The determination of the mass composition of the highest energy cosmic rays is one of the greatest challenges in cosmic ray experiments. The highest energy cosmic rays are only detected indirectly because of their very low flux. Using the atmosphere as a large target, Air Fluorescence Detectors are capable of tracing the evolution of the size of the Extensive Air Shower through the atmosphere (the shower longitudinal profile). The analysis of the characteristics of the detected longitudinal profiles is currently the most reliable way for extracting some information about the primary cosmic ray mass composition. In this proceeding, I will describe in some detail the Pierre Auger elongation rate studies, and I will show the potential for mass composition studies using the surface and the fluorescence detectors information as part of a single analysis. The interpretation of the current data with regard to mass composition, relies heavily on high energy hadron interaction models. Using standard hadron interaction models, the data suggest that the composition becomes lighter up to about 2 $\times$ 10$^{18}$ $eV$ and above that it becomes heavier again. This apparent change in the mass composition at 2 $\times$ 10$^{18}$ $eV$ seems to be correlated with a spectrum index change in the observed energy spectrum.