Charm quark
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| Composition: | Elementary particle |
| Family: | Fermion |
| Group: | Quark |
| Generation: | Second |
| Interaction: | Strong, Weak, Electromagnetic force, Gravity |
| Antiparticle: | Charm antiquark (c) |
| Theorized: | Sheldon Glashow, John Iliopoulos, Luciano Maiani (1970) |
| Discovered: | Samuel C.C. Ting et al. (1974) Burton Richter et al. (1974) |
| Symbol(s): | c |
| Mass: | 1.16–1.34 GeV/c2 |
| Decays into: | Strange quark, down quark |
| Electric charge: | +2⁄3 e |
| Color charge: | Yes |
| Spin: | 1⁄2 |
Flavour quantum numbers:
Combinations:
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The charm quark is a second-generation quark with an electric charge of +2⁄3 e. It is the fourth most massive of the quarks, at about 1.5 GeV/c2 (roughly one and a half times the mass of the proton). The existence of a fourth quark had been speculated by a number of authors around 1964 (see for instance Bjorken and Glashow[1]). Its prediction in more modern form is usually credited to Glashow, Iliopoulos and Maiani[2], in 1970. It was first observed in November 1974, with the simultaneous discovery of the J/ψ charm particle at SLAC (Stanford Linear Accelerator Center) by a group led by Burton Richter[3] and at BNL (Brookhaven National Laboratory) by a group led by Samuel C. C. Ting.[4] The particle was named J by the BNL group and ψ by the SLAC group; when the naming controversy could not be resolved, the compromise J/ψ was adopted.
[edit] Hadrons containing charm quarks
Some of the hadrons containing charm quarks include:
- D mesons contain a charm quark (or its antiparticle) and an up or down quark.
- Ds mesons contain a charm quark and a strange quark.
- There are many charmonium states, for example the J/ψ particle. These consist of a charm quark and its antiparticle.
- Charmed baryons have been observed, and are named in analogy with strange baryons (e.g. Λ+c).
[edit] Notes
- ^ Bjorken, B.J; Glashow, S.L. (1964). "Elementary particles and SU(4)". Physics Letters 11: 255-257. doi:.
- ^ Glashow, S.L.; Iliopoulous, J.; Maiani, L. (1970). "Weak Interactions with Lepton–Hadron Symmetry". Physical Review D 2: 1285-1292. doi:.
- ^ Augustin, J.-E.; et al. (1974). "Discovery of a Narrow Resonance in e+e− Annihilation". Physical Review Letters 33: 1406. doi:.
- ^ Aubert, J.J. (1974). "Experimental Observation of a Heavy Particle J". Physical Review Letters 33: 1404. doi:.
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