On 1 September, scientists on the LUX-ZEPLIN experiment reported a single particle interaction that does not match the backgrounds they know how to account for. They presented it at the TeV Particle Astrophysics meeting in Japan. It is not a discovery. The result is 2.6 sigma. In plain terms, there is about a 0.5 percent chance it is ordinary noise. Physics usually waits for 5 sigma before anyone pops champagne.
LZ sits nearly a mile underground at the Sanford Underground Research Facility in South Dakota. It watches 10 tonnes of liquid xenon for weakly interacting massive particles, or WIMPs, a leading dark-matter candidate. The collaboration of 250 researchers from 39 labs analyzed 220 live days of data from March 2023 to April 2024. They had already looked in that data for the simplest WIMP recoil. This pass looked for a higher-energy kind of kick.
If the flash was dark matter, the particle would likely weigh at least 200 times a proton, and it would not be the textbook WIMP they first went hunting for. Professor Sergey Burdin of the University of Liverpool, on the team since 2014, called the event exciting and said it still might be a rare background they do not yet understand.
LZ has more data on disk and will keep running into 2028. One event is a hint. The next events, or the lack of them, will decide if it was a particle or a Friday.
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