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2w ago

LZ Reports Single Anomalous Event That Fits Heavy WIMP Models

Reporting a lone high-energy nuclear recoil consistent with heavy WIMP models, LZ seeks internal checks as well as independent confirmation

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

  • A reanalysis of 220 live days of LUX‑ZEPLIN data collected between March 2023 and April 2024 turned up one unexplained high-energy nuclear recoil that the team flagged as an outlier.
  • Lead analysts say the event matches signatures expected from a heavy WIMP, where a WIMP is a hypothetical weakly interacting massive particle that would collide with an atomic nucleus rather than electrons.
  • The result carries about 2.6 sigma statistical significance, far below the 5 sigma standard normally required in particle physics to claim a discovery.
  • LZ presented the finding at the TeV Particle Astrophysics conference, has submitted a paper to Physical Review Letters, and is running further internal background checks while analyzing more data already collected.
  • Researchers warn the blip could be an unmodeled background revealed by the detector’s greater sensitivity and say independent confirmation by other xenon experiments would be needed before treating this as evidence of dark matter.