基于新升级的西藏 ASγ新联合实验开展原初宇宙线铁核能谱算法的研究

高能宇宙线的起源及加速问题，被列为21世纪11个重大前沿科学难题之一，至今没有得到有效解决。由于不同的宇宙线起源理论预言不同的宇宙线单成分能谱结构及核种成分比例，因此精确测量宇宙线各单成分能谱的精细结构，是判断宇宙线起源问题的一把关键钥匙。为了精确测量“膝”区宇宙线各单成分能谱及其精细结构，西藏ASγ实验近年来完成了对实验设备大规模的升级改造，升级之后的ASγ新联合实验已成为目前国际上对“膝”区宇宙线成分研究灵敏度最高的实验，并已于2014年3月正式运行。本项目拟以ASγ新联合实验为基础，开展“膝”区宇宙线铁谱算法分析的计算机蒙卡模拟研究，拟从两个方面形成突破：1) 创新性地开发出适合铁核的空气簇射横向密度分布函数（NKG函数），以提高铁核的能量分辨率；2)开发多变量解析算法，充分优化神经元网络、随机森林等方法，以提高铁核的分离精度。力争所求铁谱在精细结构及“膝”的位置精度上获得较大提高。

The origin of high-energy cosmic rays is considered one of the 21st century 11 critical scientific problems, and it has not been solved effectively so far. Considering that the different origin mechanisms of cosmic rays will predict different energy spectra of individual components and different chemical compositions, precise measurements of the energy spectrum and chemical composition of cosmic rays can be key pieces of information for probing their origin, acceleration, and propagation mechanism. In order to measure the energy spectra and chemical composition of the "knee" energy region precisely, the Tibet ASγ Collaboration has upgraded the experimental equipment on a large scale. The newly updated Tibet ASγ hybrid experiment has become the most sensitive experiment for the study of cosmic-ray chemical composition at the "knee" energy region so far, and it has been running since March 2014. ..This project, based on the new Tibet ASγ hybrid experiment, focuses on optimizing and developing the new analysis algorithms for the primary cosmic-ray spectrum of iron at the "knee" energy region by carrying a detailed Monte Carlo simulation. Through optimizing the reconstruction of data analysis and developing the lateral density distribution function (NKG function) of air shower for iron nuclei especially, we can improve the energy resolution of iron. At the same time, the precision of iron identification will be improved by developing the new algorithms of multivariable analysis, and optimizing the artificial neural network (ANN) method and Random Forests (RF) method may further improve the quality of separation. With the higher energy resolution and better quality of iron separation, this project is expected to make great process at fine structure and position of iron "knee", for the final obtained iron spectrum.