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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 |
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The charm quark is a second-generation quark with an electric charge of +2⁄3 e. It is the third most massive of the quarks, at about 1.5 GeV/c2 (roughly one and a half times the mass of the proton). It was predicted in 1970 by Sheldon Glashow, John Iliopoulos, and Luciano Maiani, and first observed in November 1974, with the simultaneous discovery of the J/ψ charm particle at SLAC (Stanford Linear Accererator Center) by a group led by Burton Richter1 and at BNL (Brookhaven National Laboratory) by a group led by Samuel C. C. Ting.2 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. The quark itself derived its name from the "charmed" life the J/ψ leads, having a half-life a thousand times longer than had been predicted theoretically.
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).
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Wikipedia content modification information:
- This page was last modified on 12 November 2008, at 22:26.
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