Editing Eightfold way (physics) (section)

==Background==
By 1947, physicists believed that they had a good understanding of what the smallest bits of matter were. There were [[electron]]s, [[proton]]s, [[neutron]]s, and [[photon]]s (the components that make up the vast part of everyday experience such as [[macroscopic scale|visible matter]] and light) along with a handful of unstable (i.e., they undergo [[radioactive decay]]) exotic particles needed to explain [[cosmic ray]]s observations such as [[pion]]s, [[muon]]s and the hypothesized [[neutrino]]s. In addition, the discovery of the [[positron]] suggested there could be [[anti-particle]]s for each of them. It was known a "[[strong interaction]]" must exist to overcome [[Coulomb's law|electrostatic repulsion]] in atomic nuclei. Not all particles are influenced by this strong force; but those that are, are dubbed "hadrons"; these are now further classified as [[meson]]s (from the Greek for "intermediate") and [[baryon]]s (from the Greek for "heavy").

But the discovery of the neutral [[kaon]] in late 1947 and the subsequent discovery of a positively charged kaon in 1949 extended the meson family in an unexpected way, and in 1950 the [[lambda particle]] did the same thing for the baryon family. These particles decay much more slowly than they are produced, a hint that there are two different physical processes involved. This was first suggested by [[Abraham Pais]] in 1952. In 1953, [[Murray Gell-Mann]] and a collaboration in Japan, Tadao Nakano with [[Kazuhiko Nishijima]], independently suggested a new conserved value now known as "[[strangeness]]" during their attempts to understand the growing collection of known particles.<ref name=Gell-Mann-1953-11/><ref name=Nakano-Nishijima-1953-11/>{{efn|
A footnote in Nakano and Nishijima's paper says
{{blockquote|After the completion of this work, the authors knew in a private letter from Prof.&nbsp;Nambu to Prof.&nbsp;Hayakawa that Dr.&nbsp;Gell-Mann has also developed a similar theory.}}
}}
The discovery of new mesons and baryons continued through the 1950s; the number of known "elementary" particles ballooned. Physicists were interested in understanding hadron-hadron interactions via the strong interaction. The concept of [[isospin]], introduced in 1932 by [[Werner Heisenberg]] shortly after the discovery of the neutron, was used to group some hadrons together into "multiplets" but no successful scientific theory as yet covered the hadrons as a whole. This was the beginning of a chaotic period in particle physics that has become known as the "[[particle zoo]]" era. The eightfold way represented a step out of this confusion and towards the [[quark model]], which proved to be the solution.