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Unidentified falling objects in the LHC as dark matter signals

Xunyu Liang* and Ariel Zhitnitsky†

  • *Contact author: xunyul@phas.ubc.ca
  • †Contact author: arz@phas.ubc.ca
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Phys. Rev. D 114, 036001 – Published 3 August, 2026

DOI: https://doi.org/10.1103/dm21-8tvz

Abstract

Unidentified falling objects (UFOs) refer to sporadic beam losses observed during LHC operation. The prevailing explanation is that micrometer-sized dust particles released from the beam screen produce beam losses through interactions with the protons. However, the release mechanism of these particles remains unknown. We propose that roughly (1–10)% of UFOs may be caused by axion quark nuggets (AQNs), macroscopic dark matter (DM) candidates with masses of order (5–1000) g. The AQN model naturally relates the dark and visible matter abundances (ΩDM∼Ωvisible) and provides a mechanism for generating the baryon-antibaryon asymmetry, with DM composed of both matter and antimatter AQNs. When passing underground within approximately 100 km of the LHC, an antimatter AQN generates acoustic waves strong enough to trigger multiple UFO events within 2 s. If three correlated UFOs (placed at different locations along the LHC ring) are detected, the signal-to-noise ratio can exceed 5 across the entire allowed AQN mass range for a measurement time of about 360 h. Practically, the LHC can serve as a large broadband acoustic detector for AQNs.

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Phys. Rev. D 114, 036001– Published 3 August, 2026
  • Received 26 February 2026
  • Accepted 18 June 2026
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