The angular resolution of an extensive air shower (EAS) array plays a critical role in determining its sensitivity for the detection of point γ-ray sources in the multi-TeV energy range. The GRAPES-3, an EAS array located at Ooty in India (11.4oN, 76.7oE, 2200 m altitude) is designed to study γ-rays in the TeV-PeV energy range. It comprises of a dense array of 400 plastic scintillators deployed over an area of 25000 m2 and a large area (560 m2) muon telescope. The development of a new statistical method has allowed the real time determination of propagation delay of each detector in the GRAPES-3 array. The shape of the shower front is known to be curved and here the details of a new method developed for accurate measurement of the shower front curvature is presented. These two developments have led to a sizable improvement in the angular resolution of the GRAPES-3 array. It is shown that the curvature depends on the size and the age of an EAS. By employing two different techniques, namely, the odd-even and the left-right methods, independent estimates of the angular resolution are obtained. The odd-even method estimates the best achievable resolution of the array. For obtaining the angular resolution, the left-right method is used after implementing the size and age dependent curvature correction. A comparison of the angular resolution as a function of EAS energy by these two methods shows them be virtually indistinguishable. The angular resolution of the GRAPES-3 array is 47' for energies E>5 TeV and improves to 17' at E>100 TeV, eventually approaching 10' at E>500 TeV.

中文翻译：

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GRAPES-3 EAS阵列基于年龄和尺寸改进定时和阵雨锋曲率校正后的角分辨率

大范围空气淋浴 (EAS) 阵列的角分辨率在确定其检测多 TeV 能量范围内点 γ 射线源的灵敏度方面起着至关重要的作用。GRAPES-3 是位于印度 Ooty（11.4oN，76.7oE，2200 m 海拔）的 EAS 阵列，旨在研究 TeV-PeV 能量范围内的 γ 射线。它由部署在 25000 平方米区域内的 400 个塑料闪烁体的密集阵列和一个大面积（560 平方米）μ 子望远镜组成。新统计方法的开发允许实时确定 GRAPES-3 阵列中每个探测器的传播延迟。已知花洒前部的形状是弯曲的，这里介绍了一种为精确测量花洒前部曲率而开发的新方法的详细信息。这两项发展使 GRAPES-3 阵列的角分辨率有了相当大的改进。结果表明，曲率取决于 EAS 的大小和年龄。通过采用两种不同的技术，即奇偶方法和左右方法，可以获得角分辨率的独立估计。奇偶方法估计阵列的最佳可实现分辨率。为了获得角分辨率，在实施尺寸和年龄相关曲率校正后使用左右方法。通过这两种方法比较作为 EAS 能量函数的角分辨率表明它们几乎无法区分。GRAPES-3 阵列的角分辨率在能量 E>5 TeV 时为 47'，在 E>100 TeV 时提高到 17'，最终在 E>500 TeV 时接近 10'。