Strange quark
Composition:	Elementary particle
Family:	Fermion
Group:	Quark
Generation:	Second
Interaction:	Strong, Weak, Electromagnetic force, Gravity
Antiparticle:	Strange antiquark (s)
Theorized:	Murray Gell-Mann (1964) George Zweig (1964)
Symbol(s):	s
Mass:	70–130 MeV/c2
Decays into:	Up quark
Electric charge:	−1⁄3 e
Color charge:	Yes
Spin:	1⁄2

The strange quark is a second-generation quark with a charge of −(1/3)e and a strangeness of −1. It is the third-lightest quark after the up and down quarks, with a mass of somewhere between 80 and 130 MeV. The first strange particle (particle containing a strange-valence quark) was discovered in 1947, with the identification of the kaon, but the strange quark itself was not identified until Gell-Mann and Zweig developed the quark model in 1964.

Hadrons containing strange-valence quarks

Hadrons containing strange-valence quarks include the following:

• Kaons are mesons containing a strange quark (or its antiparticle) and an up or down quark.
• The η and η′ flavorless mesons are linear combinations of several quark-antiquark pairs, including the strange-antistrange.
• The φ flavorless meson is pure strange-antistrange.
• Strange baryons are known as hyperons: the Σs and Λs have one strange quark, the Ξs two, and the Ωs three.

See also

• Strange matter
• Strange star
• Strangelet

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