the existence of up, down and strange quarks which would belong to the fundamental representation of the SU(3) flavor symmetry. GIM-Mechanism and charm To explain the observed absence of flavor-changing neutral currents, the GIM mechanism was proposed in 1970, which introduced the charm quark and predicted the J/psi meson. The J/psi meson was indeed found in 1974, which confirmed the existence of charm quarks. This discovery is known as the November Revolution. The flavor quantum number associated with the charm quark became known as charm. Bottomness and topness The bottom and top quarks were predicted in 1973 in order to explain CP violation, which also implied two new flavor quantum numbers: bottomness and topness. See also Standard Model (mathematical formulation) Cabibbo–Kobayashi–Maskawa matrix Strong CP problem and chirality (physics) Chiral symmetry breaking and quark matter Quark flavour tagging, such as B-tagging, is an example of particle identification in experimental particle physics. References Further reading Lessons in Particle Physics Luis Anchordoqui and Francis Halzen, University of Wisconsin, 18th Dec. 2009 External links The particle data group. Physical quantities Standard Model Quantum chromodynamics Quark matter Conservation laws