|Interactions||Strong, Weak, Electromagnetic force, Gravity|
|Antiparticle||Strange antiquark (s)|
Murray Gell-Mann (1964)
George Zweig (1964)
−5 MeV/c2 95
|Decays into||Up quark|
|Electric charge||–1⁄3 e|
|Weak isospin||LH: −1⁄2, RH: 0|
|Weak hypercharge||LH: 1⁄3, RH: −2⁄3|
The strange quark or s quark (from its symbol, s) is the third-lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Example of hadrons containing strange quarks include kaons (K), strange D mesons (D
s), Sigma baryons (Σ), and other strange particles.
Along with the charm quark, it is part of the second generation of matter, and has an electric charge of −1⁄3 e and a bare mass of +5
−5 MeV/c2. Like all 95quarks, the strange quark is an elementary fermion with spin-1⁄2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. The antiparticle of the strange quark is the strange antiquark (sometimes called antistrange quark or simply antistrange), which differs from it only in that some of its properties have equal magnitude but opposite sign.
The first Eightfold Way classification scheme of hadrons. The first evidence for the existence of quarks came in 1968, in deep inelastic scattering experiments at the Stanford Linear Accelerator Center. These experiments confirmed the existence of up and down quarks, and by extension, strange quarks, as they were required to explain the Eightfold Way.
- History 1
- See also 2
- References 3
- Further reading 4
In the beginnings of particle physics (first half of the 20th century), hadrons such as protons, neutron and pions were thought to be elementary particles. However, new hadrons were discovered, the 'particle zoo' grew from a few particles in the early 1930s and 1940s to several dozens of them in the 1950s. However some particles were much longer lived than others; most particles decayed through the strong interaction and had lifetimes of around 10−23 seconds. But when they decayed through the weak interactions, they had lifetimes of around 10−10 seconds to decay. While studying these decays Murray Gell-Mann (in 1953) and Kazuhiko Nishijima (in 1955) developed the concept of strangeness (which Nishijima called eta-charge, after the eta meson (η)) which explained the 'strangeness' of the longer-lived particles. The Gell-Mann–Nishijima formula is the result of these efforts to understand strange decays.
However, the relationships between each particles and the physical basis behind the strangeness property was still unclear. In 1961, Gell-Mann and
- J. Beringer et al. (
- M. Gell-Mann (1953). "Isotopic Spin and New Unstable Particles".
- G. Johnson (2000). Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics.
- K. Nishijima, Kazuhiko (1955). "Charge Independence Theory of V Particles".
M. Gell-Mann (2000) . "The Eightfold Way: A theory of strong interaction symmetry". In M. Gell-Mann, Y. Ne'eman. The Eightfold Way.
Original: M. Gell-Mann (1961). "The Eightfold Way: A theory of strong interaction symmetry".
Y. Ne'eman (2000) . "Derivation of strong interactions from gauge invariance". In M. Gell-Mann, Y. Ne'eman. The Eightfold Way.
Original Y. Ne'eman (1961). "Derivation of strong interactions from gauge invariance".
- M. Gell-Mann (1964). "A Schematic Model of Baryons and Mesons".
- G. Zweig (1964). "An SU(3) Model for Strong Interaction Symmetry and its Breaking". CERN Report No.8181/Th 8419.
- G. Zweig (1964). "An SU(3) Model for Strong Interaction Symmetry and its Breaking: II". CERN Report No.8419/Th 8412.
- B. Carithers, P. Grannis (1995). "Discovery of the Top Quark" (PDF).
- E. D. Bloom; Coward, D.; Destaebler, H.; Drees, J.; Miller, G.; Mo, L.; Taylor, R.; Breidenbach, M.; et al. (1969). "High-Energy Inelastic e–p Scattering at 6° and 10°".
- M. Breidenbach; Friedman, J.; Kendall, H.; Bloom, E.; Coward, D.; Destaebler, H.; Drees, J.; Mo, L.; Taylor, R.; et al. (1969). "Observed Behavior of Highly Inelastic Electron–Proton Scattering".
- J. I. Friedman. "The Road to the Nobel Prize".
- R. P. Feynman (1969). "Very High-Energy Collisions of Hadrons".
- S. Kretzer; Lai, H.; Olness, Fredrick; Tung, W.; et al. (2004). "CTEQ6 Parton Distributions with Heavy Quark Mass Effects".
- D. J. Griffiths (1987). Introduction to Elementary Particles.
- M. E. Peskin, D. V. Schroeder (1995). An introduction to quantum field theory.
At first people were reluctant to identify the three-bodies as quarks, instead preferring Richard Feynman's parton description, but over time the quark theory became accepted (see November Revolution).
).quark model had substructure, and that protons made of three more-fundamental particles explained the data (thus confirming the protons experiments indicated that Deep inelastic scattering .Stanford Linear Accelerator Center Up and down quarks were the carriers of isospin, while the strange quark carried strangeness. While the quark model explained the Eightfold Way, no direct evidence of the existence of quarks was found until 1968 at the , then consisting only of up, down, and strange quarks.quark model (independently of each other) proposed the