LHCb Experiment Discovers A Particle With Two Heavy Quarks

Schematic representation of the new particle. CERN

The LHCb experiment at CERN has announced the discovery of a new particle with two heavy quarks. This is the first unequivocal detection of such a particle.

The new particle is called Ξcc++, and although the typeface might appear scary, it is pronounced simply as Xi-c-c-plus-plus. It is made of one up quark, which is found in everyday particles like protons and neutrons, and two charm quarks, which have the same electric charge as the up quark but weigh 570 times more each.

The team hope to study it in more detail soon in order to test the limits of the current theory of fundamental particles, known as quantum chromodynamics.

“Finding a doubly heavy-quark baryon [a particle made of three quarks] is of great interest as it will provide a unique tool to further probe quantum chromodynamics, the theory that describes the strong interaction, one of the four fundamental forces,” Giovanni Passaleva, new spokesperson of the LHCb collaboration, said in a statement. “Such particles will thus help us improve the predictive power of our theories.”

The discovery was announced at the EPS Conference on High Energy Physics in Venice. The researchers are studying how this particle behaves by looking at how stable it is and in what other particles it decays.

Particles that have so far been seen are made of, at most, one heavy quark – either a charm, strange, top, or bottom. Having a particle with two changes the dynamic of the system, which means it could exhibit some unexpected physics.

“In contrast to other baryons, in which the three quarks perform an elaborate dance around each other, a doubly heavy baryon is expected to act like a planetary system, where the two heavy quarks play the role of heavy stars orbiting one around the other, with the lighter quark orbiting around this binary system,” added Guy Wilkinson, former spokesperson of the collaboration.

The detection of such a particle was possible thanks to the high energy of the Large Hadron Collider. This has increased the chance for creating these heavier cousins of the common quarks and to study them like never before.

Researchers now hope to find more doubly-heavy particles using the particle smashers. However, very few particles will likely have a cuter description than "doubly charmed baryon". The technical name comes from Ξcc++T having two charm quarks. 

The team has submitted a paper about this discovery to Physical Review Letters and can be read here.  


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