COSINE-100 is a dark matter detection experiment that uses NaI(Tl) crystal detectors operating at the Yangyang underground laboratory in Korea since September 2016. Its main goal is to test the annual modulation observed by the DAMA/LIBRA experiment with the same target medium. Recently DAMA/LIBRA has released data with an energy threshold lowered to 1 keV, and the persistent annual modulation behavior is still observed at 9.5$\sigma$. By lowering the energy threshold for electron recoils to 1 keV, COSINE-100 annual modulation results can be compared to those of DAMA/LIBRA in a model-independent way. Additionally, the event selection methods provide an access to a few to sub-GeV dark matter particles using constant rate studies. In this article, we discuss the COSINE-100 event selection algorithm, its validation, and efficiencies near the threshold.

COSINE-100是一项暗物质检测实验，使用了自2016年9月以来在韩国阳阳地下实验室运行的NaI（Tl）晶体检测器。其主要目标是使用相同的目标介质测试DAMA / LIBRA实验观察到的年度调制。最近，DAMA / LIBRA发布了能量阈值降低到1 keV的数据，并且仍然在9.5观察到了持续的年度调制行为。$\sigma$。通过将电子反冲的能量阈值降低至1 keV，可以以模型独立的方式将COSINE-100年度调制结果与DAMA / LIBRA的结果进行比较。此外，事件选择方法还可以使用恒定速率研究提供一些进入亚GeV暗物质颗粒的通道。在本文中，我们讨论了COSINE-100事件选择算法，其验证以及接近阈值的效率。