Operation of the Telescope Array Observatory

望远镜阵列（TA）天文台是北半球最大的超高能宇宙射线（uhecr）探测器。目前正在对观测站（TAx4）进行升级，这将使部署的表面探测器（SD）的数量增加一倍，总仪器面积增加约1800平方公里。荧光检测器阵列（fd）可以忽略这个SD阵列，提供有关检测事件的重要附加信息。该奖项支持犹他大学宇宙射线物理小组操作TA天文台综合体。该合同支持该团队，包括管理、工程和技术人员，他们全权负责设施维护、人员值班和处理数据，并遵守土地管理局的土地使用规定。天文台支持辅助和测试实验，包括最近主持的闪电测绘阵列，以及通过ASPIRE项目协调的公共教育和推广计划。TA数据分析已经确定了北部天空中57 EeV以上的uhecr的“热点”，其显著性为3.5 sigma。天文台在比较热点区域内和外部的事件时，也看到了宇宙射线光谱形状不同的迹象，以及光谱在最高能量处明显的赤纬依赖性。然而，热点的来源仍然未知。南半球最大的UHECR探测器皮埃尔·奥格天文台（Pierre Auger Observatory）和TA测量结果之间的不一致，在最高能量上也很明显，包括对Xmax分布的宽度和形状的研究。通过TAx4升级操作收集的额外数据，结合最近安装的fd的能量校准，将提高仪器的灵敏度，以解决我们对宇宙中最高能量粒子的理解中这些重要的开放性问题。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Telescope Array (TA) Observatory is the largest detector of ultra-high energy cosmic rays (UHECRs) in the Northern Hemisphere. An upgrade to the observatory (TAx4) is currently underway that will double the number of deployed surface detectors (SD) over an increased total instrumented area of approximately 1800 square-km. An array of florescence detectors (FDs) overlooks this SD array, providing important additional information on the detected events. This award supports the cosmic ray physics group at the University of Utah in operating the TA Observatory complex. The award supports the team, including managerial, engineering and technical staff, who have sole responsibility for facility maintenance, staffing observing shifts and handling data, and maintaining compliance with Bureau of Land Management land use regulations. The observatory supports auxiliary and test experiments, including recently hosting a lightning mapping array, and a public education and outreach program coordinated through the ASPIRE project. TA data analyses have identified a “hotspot” of UHECRs above 57 EeV in the northern sky at 3.5 sigma significance. The observatory has also seen indications of differences in the cosmic ray spectral shape when comparing events within the hotspot region to those outside, as well as an apparent declination dependence of the spectrum at the highest energies. The source of the hotspot, however, remains unknown. Inconsistencies between the measurements of TA and the Pierre Auger Observatory, the largest UHECR detector in the southern hemisphere, are also apparent at the highest energies, including in the studies of the width and shape of the Xmax distributions. The additional data collected with the operation of the TAx4 upgrade, combined with the energy calibrations of the recently installed FDs, will improve the sensitivity of the instrument toward resolving these important open questions in our understanding of the highest energy particles in the Universe.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.