The electroweak theory of particle physics is a unification of the electromagnetic and weak interactions. Because it is a gauge field theory, the force is transmitted between matter particles by other particles known as gauge bosons. The electroweak particles are the photon, the W boson, and the Z boson. In addition, there is theHiggs boson. All matter particles (quarks and leptons) interact through the electroweak interactions.

The photon is the familiar force-carrier of electromagnetism. It is massless, electrically neutral, and interacts with all particles that carry electric charge. The only matter particles with which the photon does not interact are the three neutrinos, which are electrically neutral. Albert Einstein is usually credited with the discovery of the photon because he used its existence to explain the photoelectric effect in 1905, although Isaac Newton was the first to guess that light had a particle-like character.

The Z...