Search for Light Dark Matter–Electron Scattering in the PandaX-II Experiment
Chen Cheng, Pengwei Xie, Abdusalam Abdukerim, Wei Chen, Xun Chen, Yunhua Chen, Xiangyi Cui, Yingjie Fan, Deqing Fang, Changbo Fu, Mengting Fu, Li‐Sheng Geng, Karl Giboni, Linhui Gu, Xuyuan Guo, K. Han, Changda He, Shengming He, Di Huang, Yan Huang, Yanlin Huang, Zhou Huang, Xiangdong Ji, Yonglin Ju, Shuaijie Li, Q. Lin, Huaxuan Liu, Jianglai Liu, Liqiang Liu, Xiaoying Lu, Wenbo Ma, Y. G., Yajun Mao, Yue Meng, Parinya Namwongsa, Kaixiang Ni, Jinhua Ning, Xuyang Ning, Xiangxiang Ren, Nasir Shaheed, Changsong Shang, Guofang Shen, Lin Si, Andi Tan, Anqing Wang, Hongwei Wang, Meng Wang, Qiuhong Wang, Siguang Wang, Wei Wang, Xiuli Wang, Zhou Wang, Mengmeng Wu, Shiyong Wu, Weihao Wu, Jingkai Xia, Mengjiao Xiao, Xiang Xiao, Binbin Yan, Jijun Yang, Yong Yang, Chunxu Yu, Jumin Yuan, Ying Yuan, Xinning Zeng, Dan Zhang, Tao Zhang, Li Zhao, Qibin Zheng, Jifang Zhou, Ning Zhou, Xiaopeng Zhou
Abstract
We report constraints on light dark matter through its interactions with shell electrons in the PandaX-II liquid xenon detector with a total $46.9\text{ }\text{ }\mathrm{tonnes}/\mathrm{day}$ exposure. To effectively search for these very low energy electron recoils, ionization-only signals are selected from the data. 1821 candidates are identified within an ionization signal range between 50 and 75 photoelectrons, corresponding to a mean electronic recoil energy from 0.08 to 0.15 keV. The 90% C.L. exclusion limit on the scattering cross section between the dark matter and electron is calculated with systematic uncertainties properly taken into account. Under the assumption of point interaction, we provide the world's most stringent limit within the dark matter mass range from 15 to $30\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, with the corresponding cross section from $2.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}37}$ to $3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}38}\text{ }\text{ }{\mathrm{cm}}^{2}$.