Analysis of Data from the Telescope Array Observatory

望远镜阵列（TA）天文台是北方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，这将使部署的地面探测器（SD）数量增加一倍，增加的总仪器面积约为1800平方公里。荧光检测器（FD）阵列俯瞰该SD阵列，提供关于检测到的事件的重要附加信息。该奖项支持犹他州大学的宇宙射线物理小组分析TA天文台的数据。 该奖项包括支持博士后和研究生研究人员开展TA“热点”研究和超高能宇宙射线光谱和成分研究。 根据该奖项，该团队将继续开发一个广泛的推广计划，ASPIRE，其中包括在线网络课程和与当地社区的直接互动。TA数据分析已经确定了北方天空中高于57 EeV的UHECR的“热点”，其显著性为3.5 sigma。天文台还发现，当比较热点区域内的事件与热点区域外的事件时，宇宙射线光谱形状存在差异，并且在最高能量下光谱具有明显的递减依赖性。然而，热点的来源仍然未知。TA和皮埃尔俄歇天文台（南半球最大的UHECR探测器）的测量之间的不一致性在最高能量下也很明显，包括对Xmax分布的宽度和形状的研究。TAx 4升级收集的额外数据，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NSF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 analysis of data from the TA Observatory. The award includes support for postdoctoral and graduate student researchers carrying out studies of the TA “hot-spots” and studies of the ultra-high energy cosmic ray spectrum and composition. Under the award, the team will continue to develop a broad outreach program, ASPIRE, that includes online web lessons and direct interactions with the local community.TA data analyses have identified a “hot-spot” 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 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.