Physicists at the University of British Columbia suggest that mysterious beam-loss events inside the Large Hadron Collider, known as unidentified falling objects, could be triggered by passing macroscopic dark matter known as axion quark nuggets, potentially offering the first proposal to use the LHC to search for macroscopic, non-elementary dark matter.
For years, researchers operating the Large Hadron Collider have contended with recurring glitches in the high-energy proton beams. These sudden beam-loss occurrences, informally designated by physicists as unidentified falling objects, stem from microscopic specks of dust drifting into the beam path inside the pristine 27-kilometer circular tunnel. While physicists are reasonably certain that dust causes the disruptions, the underlying mechanism that shakes those tiny particles loose from the beam screen has remained an open question.
How Axion Quark Nuggets Could Shake the Accelerator
A fresh theoretical proposal points to a hypothetical form of dark matter called axion quark nuggets, or AQNs, as the unseen catalyst. Proposed by physicists Xunyu Liang and Ariel Zhitnitsky of the University of British Columbia, the hypothesis suggests that dense, macroscopic dark matter objects possessing masses up to about a kilogram could interact with their terrestrial surroundings through subtle acoustic vibrations.
The researchers liken the Large Hadron Collider to a gigantic and extremely delicate Swiss watch designed to maintain stability amid countless environmental disturbances. When an AQN passes through Earth within roughly 100 kilometers of the facility, the tiny underground acoustic shock wave generated by its transit could faintly rattle the accelerator enough to dislodge micron-sized specks of dust into the proton beam.
“You can think of the LHC as a gigantic and extremely delicate Swiss watch. It is built to keep running despite countless small disturbances around it.”
Xunyu Liang and Ariel Zhitnitsky, University of British Columbia
The initial inquiry began as a coincidence when the investigators noticed that the estimated size of the collider’s troublesome dust specks matched the physical scale of the AQNs they study. Although matching dimensions proved coincidental, the connection redirected their focus toward whether invisible dark matter could generate the physical force required to shake the dust loose.
“At first, we expected to find a relation between the LHC’s mysterious ‘unidentified falling objects’ and dark matter. Later, we realized that we were actually putting forward the first proposal, to the best of our knowledge, to use the LHC to search for macroscopic, non-elementary dark matter.”
Xunyu Liang and Ariel Zhitnitsky, University of British Columbia
Detecting Invisible Signals Without Hardware Upgrades
Directly identifying dark matter has historically frustrated experimental physicists because the substance barely interacts with the ordinary matter that makes up the visible universe, revealing its presence almost exclusively through gravitational effects. However, macroscopic candidates like AQNs offer a distinct interactive profile compared to individual elementary particles.
Crucially, testing this hypothesis requires no expensive machine retrofits or physical modifications to the particle accelerator.
Reevaluating Archived Data for Hidden Dark Matter Footprints
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