American and Russian physicists may have discovered a new “tetraquark” particle.

A tetraquark, in particle physics, is an exotic meson composed of four valence quarks.

Dubbed X(5568), the newly discovered tetraquark is unusual even among its exotic family members, since it can be achieved solely under artificial conditions, RSUTE.ru reported.

Data from the DZero experiment shows evidence of this particle containing four different types of quarks.

The new particle is made of a bottom quark, a strange quark, an up quark, and a down quark.

“At first we didn’t believe it was a new particle,” DZero co-spokesperson Dmitri Denisov said.

The DZero team found the new particle by picking out a unique decay signature from Tevatron data collected from 2002 to 2011, involving billions of recorded collision events.

The signal they found lurking in that data meets the so-called “five-sigma” threshold — the gold standard for discovery in particle physics. That means there is only about a 1 in 6 million chance that this is just a fluke.