1. Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China 2. School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, China
The DArk Matter Particle Explorer (DAMPE) is a space high-energy cosmic-ray detector covering a wide energy band with a high energy resolution. One of the key scientific goals of DAMPE is to carry out indirect detection of dark matter by searching for high-energy gamma-ray line structure. To promote the sensitivity of gamma-ray line search with DAMPE, it is crucial to improve the acceptance and energy resolution of gamma-ray photons. In this paper, we quantitatively proved that the photon sample with the largest ratio of acceptance to energy resolution is optimal for line search. We therefore developed a line-search sample specifically optimized for the line-search. Meanwhile, in order to increase the statistics, we also selected the so-called BGO-only photons that convert into e+e- pairs only in the BGO calorimeter. The standard, the line-search, and the BGO-only photon samples are then tested for line-search individually and collectively. The results show that a significantly improved limit could be obtained from an appropriate combination of the date sets, and the increase is about 20% for the highest case compared with using the standard sample only.
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