基于立体水切伦科夫探测器进行gamma/hadron鉴别解析方法的研究

甚高能宇宙线电子、gamma能谱的精确测量已成为目前研究暗物质的重要手段，尤其TeV能区宇宙线电子的研究可以为邻近宇宙线源的加速和传播提供有效地约束，对研究银河宇宙线的起源具有重要意义。由于空间卫星实验搭载探测器体积的限制，直接探测所覆盖的能区最高到1TeV或几个TeV，更高能区电子、gamma的观测只能依靠地面宇宙线阵列实验。由于地面探测器灵敏度的限制，1TeV能区宇宙线的背景排除率基本在97%左右，无法达到测量电子能谱的要求，为此我们开发了新型立体水切伦科夫探测器，充分发挥西藏阿里超高海拔优势，实现对空气簇射的立体、多维、超高海拔观测，进而大幅提高对甚高能电子、gamma的观测灵敏度。本项目以立体水切伦科夫探测器为基础，通过计算机蒙特卡洛全模拟，旨在优化探测器立体结构设计，并开发一套全新的gamma/hadron鉴别解析方法，进而实现宇宙线强子背景的高质量排除（99.9%@1TeV)。

The observations of very-high-energy (VHE, E>100GeV) cosmic-ray electrons and positrons (CREs) and gamma rays provide an important and unique probe for indirect dark matter detection, especially for the measurements of CREs in TeV energy region, which can provide constrains on local cosmic-ray accelerators and diffusion effects. For direct observations on satellites, the maximum energy they can cover is up to ~1TeV or a few TeV at most due to the combination of the steep CRE spectrum and their limited detection area. We may have no choice but to rely.on the ground-based extensive-air-shower (EAS) measurements to study the spectrum of CREs and gamma at higher energies. However, the existing EAS experiments only reject ~97% background hadron events at 1TeV , which prevents the measurements of CREs. So we develop a new three-dimensional water-Cherenkov detector to be operated at Ali (5700m above sea level) in Tibet, where the effective detection area could reach the maximum and the new detector is very sensitive to the separation of gamma and hadron by observing the three-dimensional information of air shower. ..This project, based on the new three-dimensional water-Cherenkov detector, focuses on optimizing the structural design of the detector (array), and developing a new analysis algorithms for gamma/hadron separation by carrying a detailed Monte Carlo simulation, so as to realize the high-quality rejection of background hadron events. The gamma/hadron separation is expected to reject more than 99.9% background hadron events at 1TeV, with more than 50% of CRE or gamma-ray events remaining, which will open a window to measure the VHE cosmic-ray electrons and positrons energy spectrum for ground-based EAS experiments.