Search for gamma-ray spectral lines with the DArk Matter Particle Explorer

基于“悟空”号卫星的伽马射线线谱搜寻

The DArk Matter Particle Explorer(DAMPE)is well suitable for searching for monochromatic and sharpγ-ray structures in the GeV-TeV range thanks to its unprecedented high energy resolution.In this work,we search forγ-ray line structures using five years of DAMPE data.To improve the sensitivity,we develop two types of dedicated data sets(including the BgoOnly data which is the first time to be used in the data analysis for the calorimeter-based gamma-ray observatories)and adopt the signal-to-noise ratio optimized regions of interest(ROIs)for different DM density profiles.No line signals or candidates are found between 10 and 300 GeV in the Galaxy.The constraints on the velocity-averaged cross section for xx→γγand the decay lifetime for x→γv,both at 95%confidence level,have been calculated and the systematic uncertainties have been taken into account.Comparing to the previous Fermi-LAT results,though DAMPE has an acceptance smaller by a factor of~10,similar constraints on the DM parameters are achieved and below 100 GeV the lower limits on the decay lifetime are even stronger by a factor of a few.Our results demonstrate the potential of high-energy-resolution observations on dark matter detection.

宇宙中的伽马射线是空间间接探测暗物质的重要研究对象之一,而GeV-TeV能区的伽马射线线谱在目前已知的所有天体物理机制中均不可能产生,如果一旦发现,这将是暗物质或新物理存在的确定性证据.“悟空”号对伽马射线的接受度尽管仅为费米卫星的约1/10,但得益于优异的能量分辨本领,其在线谱探测方面具有独特的优势.为了提高线谱观测灵敏度,“悟空”号开发了两种针对性的数据集,并根据多种暗物质空间分布构建了信噪比优化的选择天区.基于前5年的观测数据,“悟空”号尽管未找到显著的伽马线谱信号,但其观测可以用来对暗物质属性进行限制:对于暗物质湮灭情形,该限制与费米卫星相当;对于暗物质衰变情形,在100 GeV以下能区的限制则比费米卫星强约1倍.该研究展示了高能量分辨探测器在暗物质搜寻方面的发现潜力.