Strange Quark

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 hadrons, which are subatomic particles. Example of hadrons containing strange quarks include kaons (K), strange D mesons (D
s), Sigma baryons (Σ), and other strange particles. The strange quark was sometimes called the sideways quark in the past.

It, along with the charm quark is part of the second generation of matter, and has an electric charge of −1⁄₃ e and a bare mass of 100+30
−20 MeV/c2. Like all quarks, 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 strange particle (a particle containing a strange quark) was discovered in 1947 (kaons), but the existence of the strange quark itself (and that of the up and down quarks) was only postulated in 1964 by Murray Gell-Mann and George Zweig to explain the 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.