The Eightfold Way is a classification scheme proposed by Murray Gell-Mann and Yuval Ne’eman that organises hadrons into groups based on their shared properties and underlying symmetries.
The scheme arranges particles, specifically the light baryons and mesons discovered before 1970, into geometric octet patterns according to properties such as electric charge and strangeness. For example, the eight lightest spin-½ baryons, including the proton, neutron, and several strange particles such as the ,
and
, can be arranged into a baryon octet on a strangeness-charge diagram, with the electric charge represented along a sloping axis (see diagram above). Similarly, nine spin-0 mesons, including the pions, kaons and etas mesons, form an octet together with an additional singlet state, producing a similar pattern on a strangeness-charge diagram.
These patterns revealed that seemingly different particles were related by an underlying symmetry and suggested that they were not fundamental particles themselves, but rather combinations of more basic constituents. Specifically, Gell-Mann found that the eightfold way classification of the baryons and mesons could be explained using the SU(3) symmetry group. This idea ultimately led to the quark model, in which baryons are composed of three quarks and mesons are composed of a quark and an antiquark.