Surprising Signal in the XENON1T Dark Matter Experiment

The core of XENON1T © XENON Collaboration Scientists from the international XENON collaboration under participation of the University of Münster announced today that data from their XENON1T, the world's most sensitive dark matter experiment, show a surprising excess of events. The scientists do not claim to have found dark matter. Instead, they say to have observed an unexpected rate of events, the source of which is not yet fully understood. The signature of the excess is similar to what might result from a tiny residual amount of tritium (super heavy hydrogen), but could also be a sign of something more exciting: the existence of a new particle known as the solar axion or the indication of previously unknown properties of neutrinos. XENON1T was operated deep underground at the INFN Laboratori Nazionali del Gran Sasso in Italy, from 2016 to end of 2018. It was primarily designed to detect dark matter, which makes up 85% of the matter in the universe and for which there is only indirect evidence so far. XENON1T didn't detect dark matter, but has reached the world-leading sensitivity for the search for WIMPs (Weakly Interacting Massive Particles), which are among the theoretically preferred candidates for dark matter.