Information AboutHadron |
| CATEGORIES ABOUT HADRON | |
| hadrons | |
| nuclear physics | |
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Like all , P, the Parity , C, the C Parity , and m, the mass. In addition they may carry Flavour quantum numbers such as Isospin (or G Parity ), Strangeness etc. Hadrons can be further divided into two classes:
Most hadrons can be classified by the Quark Model which posits that all the quantum numbers of baryons are derived from those of the ''valence quarks''. For a baryon these are three Quark s and for a meson these are a quark-antiquark pair. Each quark is thus a fermion with B=1/3. Excited baryon or meson states are known as Resonance s. Each ground state hadron may have many excited states, and hundreds have been observed in particle experiments. Resonances decay extremely quickly (within about 10−24 s) via strong interactions. Mesons which lie outside the quark model classification are called Exotic Meson s. These include glueballs, '''hybrid mesons''' and '''tetraquarks'''. The only baryons which lie outside the quark model at present are the ''' Pentaquark s''', but the evidence for their existence is unclear as of 2005 . All hadrons are single particle excitations of the basic theory of Strong Interactions , called Quantum Chromodynamics . Due to a property called Confinement that this theory enjoys at energies below the QCD Scale , these excitations are not Quark s and Gluon s, which are the basic fields, but the hadrons which are composite, and carry no Color Charge . In other phases of QCD Matter the hadrons may disappear. For example, at very low temperature and low pressure, unless there are sufficiently many very massive flavors of quarks, QCD predicts that quarks and gluons will interact weakly and in particular no longer be confined. This property, which is known as Asymptotic Freedom , has been experimentally confirmed at the energy scales between a GeV and a TeV. SEE ALSO REFERENCES AND EXTERNAL LINKS
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