暗物质粒子间接探测的本底研究

In recent years the indirect detection of dark matter has gotten important progresses. The AMS-02 experiment confirmed the existence of electron/positron excess at high energies and gave a precise measurement of antiproton fraction in cosmic rays. In the end of 2015 the first Chinese astronomical satellite DAMPE was launched, which will measure the electron spectrum up to 10 TeV. It is expected that the precise measurement of electron spectrum at high energies may find some features, which can be used to find the signal of dark matter annihilation or decay. However, the largest obstacle to detect dark matter signal in the indirect detection comes from the cosmic ray background, which can never be removed. Therefore it is very important to study the cosmic ray background thoroughly and estimate the uncertainties of the cosmic ray background. In this project we will try to determine the cosmic rays propagation process precisely based on the latest data, and study the effect of solar modulation. Then we will calculate the fluxes of the secondary antiproton, positron and diffuse gamma ray which are generated by cosmic rays interaction with interstellar gas. We will also calculate the contribution of high energy electrons and positrons from nearby cosmic ray sources and discuss how to identify the source of high energy electrons. We hope these studies will provide a solid background for dark matter search in cosmic ray experiments.

近几年暗物质间接探测方面取得了重要的进展，AMS-02实验证实了宇宙线中正负电子在高能存在超出，并且精确测量了宇宙线中反质子的比例。2015年底我国发射了第一颗天文卫星DAMPE，它可以测量高能电子能谱到10TeV，希望能够通过精确测量电子能谱和谱上的结构确定暗物质信号。然而，暗物质间接探测最大的困难在于无法排除天体物理过程所产生的宇宙线本底。因此，要确定暗物质信号的前提是能够透彻研究宇宙线本底，明确本底计算的不确定性大小。在本项目中我们希望基于以上宇宙线实验的最新观测数据，精确地确定宇宙线传播模型、研究太阳调制效应；计算宇宙线产生的次级反质子、正电子、弥散伽马射线等流强和可能的误差大小；计算邻近宇宙线源对高能电子的贡献，探讨认证这些邻近源的方法。通过对这些宇宙线本底的细致研究希望能够为暗物质信号的寻找奠定基础。

利用暗物质卫星（DAMPE）探测暗物质信号的关键是对宇宙线产生的本底有准确理解，本项目既是开展这样的研究，从而深入理解宇宙线产生的信号本底。在本项目资助下，我们开展了宇宙线传播过程、临近脉冲星产生的正负电子贡献、太阳调制效应、宇宙线产生的反质子、正电子、反氦的精确本底等方面的研究。为了精确解释最新的宇宙线观测数据，我们构建了一个含慢扩散盘的更“真实”的银河系宇宙线传播模型并通过观测数据拟合了模型参数；根据最新观测重新检验了临近脉冲星对正负电子流强的贡献；依据宇宙线流强的时间依赖性研究了太阳调制效应；考虑各种模型误差重新计算了宇宙线反质子、正电子和反氦的流强，并解释了AMS-02的最新观测结果；依据最新的研究进展对暗物质探测信号进行了研究。这些研究成果加深了我们对暗物质卫星观测数据中本底的理解，有助于我们在暗物质卫星数据中寻找可能的暗物质信号。