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yesterday

LZ Detector Records Single Unexplained Event Consistent With a Heavy WIMP

The collaboration says the 2.6-sigma signal from a reanalysis of 220 live days requires further internal tests, peer review, independent replication.

This handout image obtained and released on March 18, 2025 by the ESA/Euclid/Euclid Consortium/NASA shows space telescope Euclid�s new image of examples of galaxies in different shapes, during Euclid first observations of the Deep Field areas. On March 19, 2025, the European space telescope Euclid, a veritable �detective of the dark universe� aided by AI and humans, delivered the first data from a mission designed to help unravel the mystery of dark matter and dark energy.
Image
LUX-ZEPLIN dark matter detector Credit: Matthew Kapust/Sanford Underground Research Facility
To search for dark matter, LZ uses photomultiplier tubes (shown here before installation in the detector) to capture light from particle interactions. Image credit: Matthew Kapust / Sanford Underground Research Laboratory.

Overview

  • The LUX‑ZEPLIN team reanalyzed 220 live days of data collected between March 2023 and April 2024 and found one high-energy nuclear‑recoil event that the collaboration says it cannot readily explain with known backgrounds.
  • The reported signal has a statistical strength of 2.6 sigma, which is far below the 5-sigma threshold physicists require to claim a discovery.
  • If the event were caused by dark matter it would match a weakly interacting massive particle (WIMP) of roughly 200 GeV or heavier, suggesting a heavier or less conventional interaction than the simplest WIMP models predict.
  • LZ presented the analysis at the 2026 TeV Particle Astrophysics conference, has submitted the paper for peer review, and is undertaking further background checks while preparing to analyze larger new datasets.
  • The experiment uses about 10 tonnes of ultrapure liquid xenon nearly a mile underground at the Sanford Underground Research Facility and involves roughly 250 scientists, and confirmation by other xenon detectors would be required to change the picture for particle physics.