LZ finds one unexplained 2.6-sigma event and withholds a dark-matter claim
LUX-ZEPLIN reports a single particle interaction in its liquid xenon detector that known ordinary matter backgrounds do not match. The analysis covers 220 live days from March 2023 to April 2024 and reaches 2.6 sigma, about a 0.5 per cent chance under known backgrounds; physics treats 5 sigma as a discovery. Rick Gaitskell is not claiming dark matter. The interaction sits in June 2023, and LZ already holds at least three times as much additional data.
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LZ finds one unexplained interaction at 2.6 sigma
LUX-ZEPLIN reports a single particle interaction in its liquid xenon detector that known ordinary matter backgrounds do not match. LZ's analysis covers 220 live days taken between March 2023 and April 2024 and reaches 2.6 sigma; Berkeley Lab puts that at roughly a 0.5 per cent chance under known backgrounds. Science News writes that spokesperson Rick Gaitskell of Brown University puts the same 2.6 sigma at about a 1 in 100 chance for known particles. Science News says 3 sigma is usually needed to claim evidence and 5 sigma is the bar for a detection. Rick Gaitskell is not claiming to have seen dark matter.[1], [2]
The Sanford tank holds 10 tonnes of xenon; the search widened in energy
Sanford Underground Research Facility houses the LZ detector in South Dakota; Berkeley Lab says the tank holds 10 tonnes of ultrapure liquid xenon and that 250 scientists and engineers from 39 institutions work on it. Berkeley Lab writes that this batch had already been searched for the faintest signals of the simplest interactions, and that the new pass covered a broader set of interactions that leave more energy behind. Berkeley Lab says that if dark matter is the source, the particle would carry a mass of at least 200 GeV/c², more than 200 times a proton's, and would interact in a way the simplest models do not describe. Aaron Manalaysay called it the first outlier in his career that appears valid in every way, while adding that the team is still hunting for a rare background it might have missed.[1]
Science News places the event in June 2023 and notes triple extra data
Science News writes that the interaction sits in June 2023 and that LZ has already collected at least three times as much additional data as the analysed set. Science News places the talk at the TeV Particle Astrophysics meeting in Tendo, Japan, and in a paper posted on the LZ website. Berkeley Lab writes that the paper is being submitted to Physical Review Letters after a talk at the TeV Particle Astrophysics conference in Japan. Science News says a prior low-energy search for weakly interacting massive particles, or WIMPs, on the same batch came up empty, that LZ hunts for two back-to-back light signals, and that Neal Weiner of NYU finds a June event notable for dark matter with internal energy states that favour summer collisions.[1], [2]
