Quark
A proton is composed of two up quarks, one down quark, and the gluons that mediate the forces "binding" them together. The color assignment of individual quarks is arbitrary, but all three colors must be present.
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| Composition | Elementary particle |
|---|---|
| Statistics | Fermionic |
| Generation | 1st, 2nd, 3rd |
| Interactions | Electromagnetism, gravitation, strong, weak |
| Symbol | q |
| Antiparticle | Antiquark ( q ) |
| Theorized |
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| Discovered | SLAC (c. 1968) |
| Types | 6 (up, down, strange, charm, top, and bottom) |
| Electric charge | + 2⁄3 e, − 1⁄3 e |
| Color charge | Yes |
| Spin | 1⁄2 |
| Baryon number | 1⁄3 |
A quark (/ˈkwɔːrk/ or /ˈkwɑːrk/) is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can be found only within hadrons, such as baryons (of which protons and neutrons are examples) and mesons. For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves.
Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. Quarks are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge.
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