US Physicists Discover New Elementary Particle

A team of US researchers has detected a new form of elementary particle called the "four-flavoured" tetraquark that can affect scientists' understanding of "quark matter" - the hot, dense material that existed moments after the Big Bang and may still exist in the super-dense interior of neutron stars.

For most of the history of quarks, it's seemed that all particles were made of either a quark and an antiquark or three quarks.

"This new particle is unique - a strange, charged beauty. It's the birth of a new paradigm. Particles made of four quarks - specifically, two quarks and two antiquarks - is a big change in our view of elementary particles," explained," said Indiana University physicist Daria Zieminska.

Zieminska is a lead member of the team responsible for the particle's detection by the DZero Collaboration at the US Department of Energy's Fermi National Laboratory.

Quarks are the building blocks that form subatomic particles, the most familiar of which are protons and neutrons - each composed of three quarks.

There are six types, or "flavours," of quarks: up, down, strange, charm, bottom and top. Each of these also has an antimatter counterpart.

A tetraquark is a group of four quarks, the first evidence for which was recorded by scientists on the Belle experiment in Japan in 2008. But the new tetraquark is the first quark quartet to contain four different quark flavors: up, down, strange and bottom.

The DZero experiment is also responsible for other fundamental physics discoveries, including the first observation, with the Collider-Detector at Fermilab experiment, of the elusive Higgs boson particle decaying into bottom quarks.

The discovery of the tetraquark - reported in the journal Physics Review Letters - also comes on the heels of the first observation of a pentaquark - a five-quark particle - announced last year by CERN's LHCb experiment at the Large Hadron Collider.

Zieminska is also a member of the ATLAS Experiment at CERN, the European Organisation for Nuclear Research.