Strange quark

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.

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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 Σ and Λ have one strange quark, the Ξ two, and the Ω three.

See also

• Strange matter
• Strange star
• Strangelet