According to the IUPAP, the symbol s is the official name, while "strange" is to be considered only as a mnemonic.[2] The name sideways has also been used because the s quark (but also the other three remaining quarks) has an I3 value of 0 while the u ("up") and d ("down") quarks have values of +1/2 and −1/2 respectively.[3]
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.
History
In the beginnings of particle physics (first half of the 20th century), hadrons such as protons, neutrons and pions were thought to be elementary particles. However, new hadrons were discovered and the "particle zoo" grew from a few particles in the early 1930s and 1940s to several dozens of them in the 1950s. Some particles were much longer lived than others; most particles decayed through the strong interaction and had lifetimes of around 10−23 seconds. When they decayed through the weak interactions, they had lifetimes of around 10−10 seconds. While studying these decays, Murray Gell-Mann (in 1953)[4][5] and Kazuhiko Nishijima (in 1955)[6] developed the concept of strangeness (which Nishijima called eta-charge, after the eta meson ( η )) to explain the "strangeness" of the longer-lived particles. The Gell-Mann–Nishijima formula is the result of these efforts to understand strange decays.
Despite their work, the relationships between each particle and the physical basis behind the strangeness property remained unclear. In 1961, Gell-Mann[7] and Yuval Ne'eman[8] independently proposed a hadron classification scheme called the eightfold way, also known as SU(3)flavor symmetry. This ordered hadrons into isospin multiplets. The physical basis behind both isospin and strangeness was only explained in 1964, when Gell-Mann[9] and George Zweig[10][11] independently proposed the quark model, which at that time consisted only of the up, down, and strange quarks.[12] 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 Stanford Linear Accelerator Center.[13][14]Deep inelastic scattering experiments indicated that protons had substructure, and that protons made of three more-fundamental particles explained the data (thus confirming the quark model).[15]
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Johnson, G. (2000). Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics. Random House. p. 119. ISBN978-0-679-43764-2. By the end of the summer ... [Gell-Mann] completed his first paper, 'Isotopic Spin and Curious Particles' and send it of to Physical Review. The editors hated the title, so he amended it to 'Strange Particles'. They wouldn't go for that either—never mind that almost everybody used the term—suggesting insteand [sic] 'Isotopic Spin and New Unstable Particles'.
