Quarks are a class of fermions whose members are the fundamental building blocks of hadrons. Each type of quark has a corresponding antiquark. Quarks may interact via the strong force, weak force, electromagnetic force, or gravitational force. They are characterized by properties known as flavor (up, down, charm, strange, top, or bottom) and quark color (red, blue, or green). Quarks (except for the top quark, whose short s lifetime means that it decays before it can form a meson) are permanently confined in particles by a manifestation of the strong force called the color force.
Hadrons are composed of quarks. Some of the constituents of several hadrons are given in the following table.
Curiously, quark spins appear to account for only 20-30% of the neutron and proton spins (Jaffe 1995, Hellemans 1996).
Color Force, Fermion, Flavor, Hadron, Kobayashi-Maskawa Matrix, Quark Color
References
Allday, J. Quarks, Leptons, and the Big Bang. IOP Press, 1998.
Jaffe, R. L. "Where Does the Proton Really Get Its Spin?" Physics Today 48, 24-30, Sept. 1995.
Hellemans, A. "Quark Studies Put Theorists in a Spin." Science 271, 911, 1996.
