hypothetical particle that is postulated to be the carrier particle, or boson, of the Higgs field, a theoretical field that permeates space and endows all elementary subatomic particles (subatomic particle) with mass through its interactions with them. The field and the particle—named after Peter Higgs of the University of Edinburgh, one of the physicists who first proposed this mechanism—provide a testable hypothesis for the origin of mass in elementary particles.

The Higgs field is different from other fundamental fields—such as the electromagnetic field—that underlie the basic forces between particles. First, it is a scalar field—i.e., it has magnitude but no direction. This implies that its carrier, the Higgs boson, has an intrinsic angular momentum, or spin, of 0, unlike the carriers of the force fields, which have spin. Second, the Higgs field has the unusual property that its energy is higher when the field is zero than when it is nonzero. The elementary particles therefore acquired their masses through interactions with a nonzero Higgs field only when the universe cooled and became less energetic in the aftermath of the big bang (big-bang model) (the hypothetical primal explosion in which the universe originated). The variety of masses characterizing the elementary subatomic particles arises because different particles have different strengths of interaction with the Higgs field.

The Higgs mechanism has a key role in the electroweak theory, which unifies interactions via the weak force and the electromagnetic force (electromagnetism). It explains why the carriers of the weak force, the W particles (W particle) and the Z particles (Z particle), are heavy, while the carrier of the electromagnetic force, the photon, has a mass of zero. However, there is as yet no experimental evidence for the Higgs boson, which would be a direct indication for the existence of the Higgs field. There is little theoretical guidance as to the mass of the particle, except that it should not be much more than one teraelectron volt (trillion electron volts (electron volt); TeV). It is also possible that there is more than one type of Higgs particle. Experiments are conducted to search for the massive Higgs particles in the highest-energy particle-accelerator (particle accelerator) colliders, in particular the Tevatron at the Fermi National Accelerator Laboratory and the Large Hadron Collider at CERN (European Organization for Nuclear Research).