'UFOs' in The Large Hadron Collider May Be Hints of Dark Matter
The CMS detector at CERN's Large Hadron Collider.
For years, strange signals have been emerging from inside the Large Hadron Collider.
Physicists call them UFOs – not extraterrestrial aircraft, but unidentified falling objects. They're strange glitches in the proton beam, sudden beam-loss events that physicists are reasonably certain are caused by microscopic dust drifting into the beam.
But the Large Hadron Collider (LHC) is about as pristine an instrument as physicists can build. The mystery is: What shakes the dust loose?
According to physicists Xunyu Liang and Ariel Zhitnitsky of the University of British Columbia in Canada, one of the biggest question marks in the Universe could be responsible.
Dark matter.
"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," Liang and Zhitnitsky told ScienceAlert.
"In our idea, a piece of dark matter passing through the Earth tens of kilometers away could create a tiny vibration, like someone lightly tapping the table under the watch. That vibration could travel to the LHC and shake loose a microscopic piece of dust inside it. If the dust then drifted into the proton beam, it could disrupt the machine and cause a beam-loss event."
The idea didn't originate with tiny, dark matter-induced shock waves.
Liang and Zhitnitsky study a hypothetical form of dark matter called axion quark nuggets, or AQNs. When they learned that the LHC's UFOs were thought to be the result of dust, one detail snagged their attention.
The specks of dust were estimated to be micron-sized – which is about the same size as the AQNs they study.
At first, they wondered whether the mysterious 'falling objects' might actually be AQNs. That turned out to be a dead end – the size match between the two was just a coincidence.
But the false lead ignited a new question: If AQNs aren't the dust itself, could they be the force that dislodges the dust from the beam screen?
No LHC upgrades would be required to search for dark matter.
(CERN)
"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," Liang and Zhitnitsky said.
"It is an amusing example of how a scientific idea can originate from an initial misconception and then develop into a serious research question."
To explore their idea, the pair naturally turned to physics.
We don't know what dark matter actually is. It barely interacts with the normal matter that the visible Universe is made of; we only know of its existence because of its gravitational effects.
Those effects show that dark matter is everywhere, but because it barely interacts with ordinary matter, it has remained frustratingly difficult to detect directly.
One hypothetical exception is AQNs – dense, macroscopic objects with masses up to about a kilogram (2.2 pounds) that could interact with their surroundings in ways individual dark matter particles do not.
The idea is speculative, but the researchers argue that, if an AQN passed through Earth within around 100 kilometers (62 miles) of the LHC, the tiny underground acoustic shock wave generated by its passage could very faintly shake the accelerator.
This shaking could be enough to rattle a few specks of dust into the proton beam, triggering a beam-loss event.
These signals, the team calculated, would be about five times stronger than background noise.
They would produce a distinctive pattern that scientists could identify as the fingerprint of an AQN event: three or more correlated UFOs within 2 seconds of each other at successive points along the 27-kilometer (17-mile) LHC tunnel.
And the search could happen now, without any additional hardware or modifications required to the existing facility.
"What makes our case especially appealing is that the LHC already has excellent monitoring systems built in, the beam-loss monitors, that were installed for a totally different reason (protecting the machine from damage)," Liang and Zhitnitsky said.
"It turns out they may also be sensitive to something no one designed them to detect."
The pair has not searched existing LHC records themselves. Instead, the paper is intended to motivate a reanalysis of past UFO events to see whether the predicted bursts are already hiding in the data – and to inspire dedicated campaigns in the future.
The approach might not be limited to the LHC either. Other particle accelerators, if large enough, could also possibly detect these AQN events, forming a global acoustic detector network.
Related: Scientists Witness Lead Literally Turn Into Gold in The Large Hadron Collider
"It would meaningfully broaden the landscape of dark matter research. Much of the field has understandably focused on microscopic elementary particles, while macroscopic, non-elementary candidates remain comparatively under-explored," they told ScienceAlert.
"A detection of correlated UFO events would offer compelling support for a macroscopic-object explanation, and would encourage the community to consider a wider range of dark-matter candidates alongside the elementary-particle picture."
{ https://www.sciencealert.com/ }
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