New experimental evidence of a class of particles known as ‘pentaquarks’ aligns with Murray Gell-Mann’s 1964 theory of matter, and raises questions of yet-to-be discovered particle states.
Physicists working at CERN’s Large Hadron Collider announced, this week, that they’d found experimental evidence of a sub-atomic particle class consisting of four quarks and one anti-quark. This particular grouping of the smallest known units of matter has, until now, been recognized as a theoretical possibility, but was never confirmed.
“This is part of a long process of discovery of particle states,” Gell-Mann said. “Every baryon is composed mostly of three quarks. Also, part of the time, it’s three quarks and a pair. What they [seem to have found] here is a particle that’s part of the time made of three quarks and a pair, and not just three quarks, which would be conventional.
[In the future] they may find more and more of them, made of quarks and anti-quarks and various combinations. And also gluons. There may be a particle that shows up that’s made of gluons and no quarks.”
Gell-Mann and George Zweig independently proposed the existence of quarks in 1964, as the fundamental building blocks of protons and neutrons. Originally recognized as mathematical constructs that explained regularities in the results of early particle-scattering experiments, the existence of quarks as physical entities was later confirmed by experiment in the 1970's.
The quark model holds that a certain category of particles is comprised of three fractionally-charged quarks, while another category is made of quark-antiquark pairs. The recent CERN discovery provides the first evidence of a ‘pentaquark’ that combines these fundamental states.
The CERN researchers have submitted their findings to the journal Physical Review Letters.
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