First Detection of Double Electron Capture in 124Xe with XENON1T

The XENON1T experiment at the LNGS opened the era of tonne-scale dark matter detectors and obtained the world’s strongest constraint on the WIMP-nucleon cross section. The investigation of additional physics channels has led, among several other results, to the first observation of the double electron capture process of 124Xe. This is the rarest decay process ever directly observed in nature, with half-life of 1.8×1022 years. The next phase of the project, XENONnT, will push forward the sensitivity to dark matter search and other rare processes by more than one order of magnitude, thanks to further background reduction, increased active xenon mass and total exposure.