Editing Charm quark (section)

=== Background ===
{{see also|Quark model}}
In 1961, [[Murray Gell-Mann]] introduced the [[Eightfold way (physics)|Eightfold Way]] as a pattern to group [[baryon]]s and [[meson]]s.{{sfn|Griffiths|2008|p=35}} In 1964, Gell-Mann and [[George Zweig]] independently proposed that all [[hadron]]s are composed of elementary constituents, which Gell-Mann called "quarks".{{sfn|Griffiths|2008|p=37}} Initially, only the [[up quark]], the [[down quark]], and the [[strange quark]] were proposed.{{sfn|Griffiths|2008|p=39}} These quarks would produce all of the particles in the Eightfold Way.{{sfn|Griffiths|2008|p=41}} Gell-Mann and [[Kazuhiko Nishijima]] had established [[strangeness]], a quantum number, in 1953 to describe processes involving [[strange particle]]s such as {{subatomic particle|Sigma|link=yes}} and&nbsp;{{subatomic particle|Lambda|link=yes}}.{{sfn|Griffiths|2008|p=34}}