The International Collaboration at the Large Hadron Collider (LHC) observed three previously unseen particles: a new type of pentaquark and the first-ever pair of tetraquarks containing a new type of tetraquark. The results, presented today at the CERN symposium, add three new extraterrestrial members to the growing list of new hadrons found at the LHC. They will help physicists better understand how quarks are bound together in these composite particles.
Quarks are elementary particles. They come in six flavors: up, down, charming, exotic, up and down. They usually combine in binary and triple groups to form hadrons like protons and neutrons that form atomic nuclei. However, it can also rarely combine into particles of four quarks and five quarks, or “quaternary quarks” and “pentaquarks”. Theorists predicted these strange hadrons at the same time as conventional hadrons about six decades ago, but only recently, in the last 20 years, have they been observed by the LHCb and other experiments.
Most of the exotic hadrons discovered in the last two decades are tetraquarks or pentaquarks, containing a charm quark and a charm antiquark, leaving two or three subatomic particles to be an up, down, or odd quark. But in the last two years, LHCb has discovered different types of exotic hadrons. Two years ago, the collaboration discovered a quaternary quark made up of two charm quarks and two charm quarks, and two charming open quarks made up of a charm antiquark, an up quark, a down quark, and a strange antiquark exist. And last year I stumbled across the first-ever example of a double open magic quadrant with two charm quarks and one up-and-down antiquark. Open magic means that the particle contains a charm quark without an equivalent antiquark.
The discoveries announced today by the LHCb collaboration include new types of exotic hadrons. The first type observed when analyzing the “decay” of negatively charged B mesons is a pentagon composed of a charm quark, a charm quark, an up quark, a down quark, and a strange quark consists. It’s the first pentagon to contain a strange quark. The result is of enormous statistical significance of 15 standard deviations, far in excess of the five standard deviations required to claim observation of the particle Particle Physics.
The second type is a doubly electrically charged quadrupole. It is an open enchanting quatrain composed of a charm quarks, odd antiquarks, and up and down quarks antiquark observed with its neutral counterpart in a joint analysis of the decay of positively charged and neutral B mesons. The new tetraquarks, observed with a statistical significance of 6.5 (doubly charged particle) and 8 (neutral particle) standard deviations, represent the first time a pair of tetraquarks has been observed.
“The more analyzes we do, the more exotic hadrons we find,” says LHCb physics coordinator Nils Toning. “We are witnessing a discovery phase similar to that of the 1950s, when the discovery of the “particle zoo” of hadrons began, eventually leading to Quark The classic hadron model of the 1960s. We’re doing Particle Zoo 2.0.
“Finding new types of tetraquarks and pentaquarks and measuring their properties will help theorists develop a unified model of exotic hadrons whose exact nature is largely unknown,” says LHCb spokesman Chris Parks. “It will also help to better understand conventional hadrons.”
While a few theoretical models describe exotic hadrons as tightly bound single units of quarks, while other models view them as pairs of modular hadrons loosely bound in a molecule-like structure. Only time and further study of exotic hadrons will tell whether the grains are one or the other, or both.
A new strange particle of matter has been discovered, the tetraquark
Read more on the LHCb website: lhcb-outreach.web.cern.ch/2022 … its neutral partner /
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