ABSTRACT
The standard model describes the electromagnetic and weak interactions, unified in the so-called electro-weak theory of Glashow–Weinberg–Salam with the gauge group U(1) × SU(2) and the strong interactions, known as quantum chromodynamics with gauge group SU(3). Theory and experiment, where tested, agree very well up to about 100 GeV, the energies reached by present-day accelerators. The standard model should then be considered as an effective field theory. The theory for which the standard model describes its effective low-energy behaviour is called a unified theory. Choosing the three basic colours red, blue, and green makes a bound state of three quarks in an antisymmetric wave function, where hence all colours are different, into a colourless composite.
