Particle Astrophysics with Milagro

甚高能伽马射线是研究宇宙射线的相对论高能天体物理源的重要工具，宇宙射线在银河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、磁场和周围的光子相互作用时，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传播到地球，当被伽马射线望远镜观测时，不仅可以提供有关宇宙射线及其来源的起源和分布的基本信息，而且可以作为暗物质湮灭的伽马射线的探针。因此，它们允许研究基本的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宇宙射线抑制能力的大型接收探测器对这项研究至关重要。米拉格罗探测器使用一种新技术来探测高能伽马射线。它允许在TeV能量域中同时和连续地观察整个头顶天空。它探测高能伽马射线在大气中相互作用产生的高能粒子束，就像每个高能光子的放大器。探测是通过在装有737个光电倍增管的600万加仑水箱中对这些相对论粒子产生的光子进行采样来进行的。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，以及拒绝大多数不必要的宇宙射线簇射。它的连续操作允许观测TeV伽马射线的稳定和瞬态源。Milagro探测并测量了来自蟹状星云的伽马射线能谱;来自活动星系核（AGNS）耀变体Mrk 501和421的活动阶段的伽马射线;来自伽马射线爆发（GRB）的伽马射线能谱;来自银河系内盘区域的扩散TeV伽马射线发射的能量谱，这些伽马射线来自宇宙射线与星系盘中的物质的相互作用，以及来自银河系天鹅座臂中的TeV伽马射线源。这些观测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NSF的资助下，我们将继续对这些和其他可能的天体进行观测，并对数据进行分析。Milagro的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培训基础。UCI还有几个积极的计划，如COSMOS和Quarknet，用于向K-12教师和学生推广。我们一直参与沟通，以学校的学生在K-12水平和老年人（继续终身学习学院）。

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).