4 Chapter 1: Introduction elberg proposed the conservation of baryon number to explain the stability of protons. Experimentally, strange particles are produced on short timescales but decay relatively slowly; Pais suggested [21] that their production and decay mechanisms were different. Gell-Mann [22, 23] and Nishijima [24] expanded on this and St¨ uckelberg’s idea by positing a new conserved quantity: strangeness. Gell-Mann, and independently Ne’eman (see [25] and references therein), began to understand the proliferation of hadrons by organizing them in mul- tiplets that are representations of the group SU(3), famously predicting the existence of the Ω − baryon (discovered in 1964 [26]). Even before this particle was observed, several authors (see [27, 28] and references therein) improved upon the phenomenological Eightfold Way by boldly postulating the existence of subnuclear structure. Gell-Mann named these smaller, fundamental build- ing blocks of hadrons quarks. The quark model was initially enormously successful. By taking these con- stituents to have spin-1/2 and fractional charge 2/3 for the u and -1/3 for the d and s , the spin, charge, and strangeness of all known hadrons was under- stood. Moreover the multiplets and their mass-ordering were well described. Using current algebra techniques scaling laws were proposed [29, 30] and found [31, 32]. These two SLAC papers also found large-angle scattering from pro- tons, which, like Rutherford’s earlier experiments with atoms [14], showed decisively that nucleons have substructure. There were two problems with the quark model at this time: quarks had not been observed and some baryons apparently violated the Pauli principle.