Dark Matter Experiment Finds Unexplained Signal

The world’s most sensitive dark-matter experiment might have found a hint of the stuff — although the data it has collected so far could be a statistical fluctuation or a spurious signal. The data collected in 2017-18 by the underground XENON1T experiment have revealed an excess in the number of particles hitting its liquid xenon, with a relatively low energy. The finding suggests the possible existence of a hypothetical particle called the axion. But another possible explanation is the presence of radioactive impurities. An upgraded version of the detector called XENONnT could solve the riddle next year.