Particle Astrophysics with Milagro

高能伽马射线为研究宇宙射线的相对论高能天体物理来源提供了重要工具，宇宙射线在我们的星系和宇宙中被加速到非常高的能量。当高能宇宙射线与物质、磁场和环境光子相互作用时，它们会产生高能伽马射线和/或高能中微子。其中一些中性粒子直接到达地球，当被伽马射线望远镜观测到时，不仅可以提供关于宇宙射线的起源和分布及其来源的基本信息，而且还可以作为暗物质湮灭的伽马射线的探测器。因此，他们允许研究基本高能天体物理学以及粒子物理学。由于这些高能伽马射线的通量很小，因此具有良好指向和足够的宇宙射线排斥能力的大型接收探测器对于这项研究至关重要。Milagro探测器使用一种新技术来探测高能伽马射线。它允许同时和连续观看整个头顶的天空在TeV能量域。它探测到高能伽马射线在大气中相互作用产生的高能粒子束，这些高能粒子束就像每个高能光子的放大器。检测是通过在装有737根光电倍增管的600万加仑水箱中对这些相对论性粒子产生的光子进行采样。这些光子的脉冲高度和到达时间允许重建原始粒子的天体方向，以及拒绝大多数不需要的宇宙射线阵雨。它的连续工作允许观察稳定和瞬态TeV伽马射线源。Milagro探测并测量了蟹状星云伽马射线的能谱；来自活动星系核（AGNS）耀变体Mrk 501和421的活动期；来自伽马射线暴（GRB）；以及宇宙射线与星系盘中物质相互作用产生的银河系内盘区域的漫射TeV伽马射线发射，以及来自银河系天鹅座臂的TeV伽马射线源。这些观测结果为理解宇宙射线的起源、加速和传播提供了新的重要数据。在国家科学基金会的资助下，工作将继续完善这些和其他可能的对象的观察结果，并分析数据。Milagro实验和数据为本科生的研究经验和研究生的硬件和软件培训提供了良好的训练基础。UCI还有几个活跃的项目，如COSMOS和Quarknet，用于向K-12教师和学生推广。我们参与了与K-12年级的学生和高年级学生（持续终身学习学院）的交流。

Very high energy gamma rays provide an important tool to investigate relativistic energetic astrophysical sources of the ubiquitous cosmic rays which are accelerated in our galaxy and in the universe to very high energies. When high energy cosmic rays interact with matter, magnetic fields and ambient photons they generate high energy gamma rays and/or neutrinos of high energy. Some of these neutral particles travel directly to the earth and, when observed by gamma ray telescopes, can both provide essential information about not only the origin and distribution of cosmic rays and their sources, but also can serve as probes for gamma rays expected from the annihilation of dark matter. Thus they allow the study fundamental high energy astrophysics as well as particle physics. As the flux of these high energy gamma rays is small, large acceptance detectors with good pointing and adequate cosmic ray rejection capabilities are essential for this study. The Milagro detector uses a new technique to detect high energy gamma rays. It allows the simultaneous and continuous viewing of the entire overhead sky in the TeV energy domain. It detects the bundles of energetic particles produced by high energy gamma ray interacting in the atmosphere, which acts like an amplifier of each high energy photon. Detection occurs by sampling light photons produced by these relativistic particles in a 6 million gallon water tank instrumented with 737 photomultiplier tubes. The pulse height and arrival times of these photons permit reconstruction of the celestial direction of the original particle, as well as rejection of most of the unwanted cosmic ray showers. Its continuous operation allows observation of both steady and transient sources of TeV gamma rays. Milagro has detected and measured the energy spectrum of gamma rays from the Crab neubla; from active galactic nuclei (AGNS) blazars Mrk 501 and 421 in their active phases; from a gamma ray burster (GRB); and of diffuse TeV gamma ray emission from the inner galactic disc region from interaction of cosmic rays with matter in the galactic disc, and from TeV gamma ray sources in the Cygnus arm of the galaxy. These observations provide new and important data for the understanding of the origin, acceleration and propagation of cosmic rays. Under this NSF grant, work will continue on refining the observations of these and other possible objects, and on analyzing the data.The Milagro experiment and data have provided excellent training ground for undergraduate student research experience and for graduate student training in hardware and software. UCI also has several active programs, such as COSMOS and Quarknet , for outreach to K-12 teachers and students. We have been involved in communicating to school students at K-12 levels and to seniors (Academy of Continued Life Long learning).