Short answers, pulled from the story.
The XENON dark matter research project is a massive underground facility located 1400 meters beneath the Apennine Mountains in the Gran Sasso National Laboratory in Italy. It uses a dual phase time projection chamber filled with liquid xenon to detect Weakly Interacting Massive Particles or WIMPs that may constitute 85 percent of all matter in the universe.
The XENON collaboration is led by Italian professor of physics Elena Aprile from Columbia University and operates underground at the Gran Sasso National Laboratory in Italy. The facility is shielded by layers of water, lead, and polyethylene to protect the detector from cosmic rays and background radiation.
The XENON10 experiment began with installation at the Gran Sasso laboratory in March 2006 and analyzed 59 live days of data between October 2006 and February 2007. The results produced no WIMP signatures but placed limits on spin independent WIMP-nucleon cross sections down to below 10 to the minus 43 square centimeters for a WIMP mass of 100 GeV.
In June 2020 the XENON1T collaboration reported an excess of 285 electron recoils events which was 53 more than the expected 232 with a statistical significance of 3.5 sigma. A new analysis by XENONnT in July 2022 discarded the excess suggesting the anomaly was likely due to background effects rather than new physics.
The XENONnT experiment published its first results of its search for WIMPs on the 28th of July 2023 excluding cross sections above 10 to the minus 47 square centimeters at 28 GeV with 90 percent confidence level. This result was published jointly on the same date the LZ experiment published its first results too excluding cross sections above 10 to the minus 47 square centimeters at 36 GeV with 90 percent confidence level.