Short answers, pulled from the story.
The XENON10 experiment began its work in March 2006 deep beneath the Gran Sasso National Laboratory in Italy. The facility sits under 3100 meters of rock and water to shield it from cosmic rays.
A dual phase time projection chamber forms the heart of every XENON detector design by using liquid xenon in the bottom section and gas above it. Two arrays of photomultiplier tubes catch light signals when an external particle strikes the liquid target creating scintillation photons with a wavelength of 178 nanometers.
Full operations started in late 2020 and first science results appeared in July 2023. A new iteration called XENONnT now holds over eight tonnes of xenon gas.
In April 2019, researchers published findings about two-neutrino double electron capture within xenon-124 nuclei. They measured a half-life for this process that exceeds the current age of the universe by several orders of magnitude.
The team reported an unexplained surplus of electron recoil events totaling 285 detections which stood 53 counts higher than the expected background of 232 with a statistical significance of 3.5 sigma. A subsequent analysis released in July 2022 discarded the excess as a statistical fluctuation.