Baryons and mesons

Quarks and gluons carry color. However, the force felt between colored objects increases with the distance between the objects, like the force of a spring. Due to this property, nature only allows net-colorless objects on scales larger than 1.0 E-15 m.

Colorless objects can be produced from colored quarks in two different ways. A meson is a combination of a quark and anti-quark of the opposite color. Examples of mesons are the p, h, r and w mesons. Mesons do not last long because they have no net baryon or net lepton number and can decay. For instance a p0 meson can decay into two photons. An object made of a red, a green and a blue quark is also colorless. These are called baryons. Examples of baryons are protons and neutrons, although there are many others. One example of a baryon is the L baryon which is comprised of one up, one down and one strange quark.

Leptons and photons can exist by themselves, rather than in groups, because they have no color.

Examples     Particle physics' index