An underground darkish matter experiment, a couple of mile under Italy’s Abruzzo mountains, has detected unexplained “extra occasions,” hinting on the chance researchers have stumbled upon some tantalizing new physics. The Xenon1T experiment, because it’s identified, has a observe document for attention-grabbing physics observations. Final 12 months, it observed “the rarest event ever recorded” — however background information gathered by the machine might have gone one higher.
In a brand new examine, published on the preprint server arXiv and but to be peer-reviewed, researchers with the Xenon collaboration report a brand new, at the moment unexplainable occasion throughout the detector they do not but absolutely perceive. Now, that does not imply they’ve discovered darkish matter — this occasion could also be defined by contamination throughout the experiment — however there are two attention-grabbing prospects.
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“That is thrilling science for certain, even whether it is principally a cliffhanger of a outcome that requires extra information,” says Samuel Hinton, an astrophysicist on the College of Queensland who was not related to the examine.
The Xenon1T experiment consists of a cylindrical tank stuffed with over 6,000 kilos of liquid xenon cooled to -139 levels Fahrenheit (-95 levels Celsius). It is so far underground that it blocks out any radioactive interference that might mess with potential darkish matter measurements. Round 85% of the universe is believed to include darkish matter however it’s mysterious and invisible. We all know it exists due to its results on matter we are able to see — however we don’t know what it’s or what particles would possibly make it up.
Researchers checked out measurements taken by Xenon1T throughout a science run between February 2017 and February 2018. The quantity of occasions noticed was a lot greater than anticipated. The staff noticed 285 occasions, in opposition to an anticipated most of round 247.
“That is actually a quite stunning outcome,” mentioned Rafael Lang, affiliate professor of physics and astronomy at Purdue College and co-author on the examine, in a release.
That led the staff to ask and discover: The place did this “extra” of low-energy occasions come from? They consider there are three prospects for the surplus:
- Tritium, a uncommon hydrogen isotope, could also be an artifact within the information.
- Photo voltaic axions, a theoretical particle produced within the solar which hasn’t been detected earlier than.
- New properties detected in neutrinos, subatomic particles that cross by principally every little thing.
“The surplus is likely to be on account of small traces of tritium, however the concept that we is likely to be sitting on one thing extra unique is actually thrilling for us,” said Luca Grandi, a physicist on the College of Chicago and co-author on the examine.
Tritium does appear to kind in comparable darkish matter experiments deep underground and this could be the mundane chance, however the focus can’t be measured within the experiment. As a substitute, the researchers write, their calculations counsel tritium could be too small to account for the vitality extra.
The very best match for the info, based on the staff, is the photo voltaic axions speculation. A photo voltaic axion is a hypothetical particle generated within the core of the solar with a low mass that might assist clarify darkish matter. The vitality extra appears to level towards detection of this elusive and mysterious particle — however scientists cannot say for certain.
“If we want a abstract of your entire outcome, I’d in the mean time put virtually all my cash on tritium being the reason, however nonetheless am hopeful that it isn’t,” Hinton mentioned.
The Xenon1T detector was shut down in December 2018 and is within the strategy of getting an improve that’s extra delicate — it should comprise extra liquid xenon and a decrease radioactive background — and the researchers consider it will assist pull the outcomes aside just a little extra and provides a extra definitive reply. There’s an opportunity it should affirm these outcomes are new physics, a serious breakthrough a long time within the making. However scientists are cautious, and persistence is essential.
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