Old Fermilab Data Leads To New Tetraquark Discovery

Things start to get really weird when you get down to the subatomic level.

Back in July of 2015, scientists at the CERN laboratory stumbled upon a new type of subatomic particle called a tetraquark. This is an exotic family of particles that we don’t know all that much about, so when new information arises it’s really exciting.

Now, Fermilab’s Tevatron collider called it a day back in 2011, but data from its final run is still being analyzed and just gave us a sniff of something new. Physicists from the DZero collaboration were mining through the Tevatron data and discovered a new particle that’s likely part of the tetraquark family.

“At first we didn’t believe it was a new particle,” DZero co-spokesperson Dmitri Denisov told Symmetry magazine. “Only after we performed multiple cross-checks did we start to believe that the signal we saw could not be explained by background or known processes, but was evidence of a new particle.”

They’ve since submitted their analysis to Physical Review Letters.

As mentioned in our article from last year, the idea of tetraquarks were first proposed by Murray Gell-Mann and George Zweig back in 1964. Gell-Mann suggested that there’s no limit to how large quarks could get and insisted that pentaquarks could exist as well. Quarks are a funky little thing. They’re the smallest known components of matter (known being the operative word) and generally buddy up in groups of twos and threes.

The newly discovered tetraquark called X(5568) is even more strange than your average tetraquark… which isn’t anywhere near normal as it is. See, previously discovered tetraquarks were generally made up  of at least two quarks of the same flavor i.e. up, down, strange, charm, top and bottom. The newly discovered X(5568) is made up of four quark flavors: up, down, strange and bottom.

Courtesy: Fermilab

Courtesy: Fermilab

This weirdo was picked out by the DZero team when they notice a unique decay signature sticking out in the Tevatron data collected between 2002 and 2011. They sifted through billions of collision events and in doing so stumbled upon the “five-sigma” threshold, meaning that there’s only a 1 in 6 million chance that their discovery is a fluke. The “five-sigma” is like hitting a hole in one — it’s the gold standard for discovery in particle physics.

“The next question will be to understand how the four quarks are put together,” said DZero co-spokesperson Paul Grannis. “They could all be scrunched together in one tight ball, or they might be one pair of tightly bound quarks that revolves at some distance from the other pair.”

Further studies of tetraquarks and the newly discovered X(5568) could help physicists learn more about how subatomic particle are found together via the strong force. This is a massive deal because every little, teeny tiny discovery leads us to a greater understanding of our universe and how things works.


It’s mind-boggling and headache-inducing, but so damn cool.


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