Quarks: Charge +/- 1/3, 2/3 e
- Proposed by Gellman and Zweig, 1963
- Hadrons (protons, neutrons, ...) are made of combinations of “quarks”: u(up), d(down) & s(strange)
- Neutron: (u d d) charge = 2/3 - 1/3 - 1/3 = 0
- Proton: (u u d) charge = 2/3 + 2/3 - 1/3 = 1
Great success! Particles grouped in families made of quarks. No extra particles!