"God particle" redirects here. For the book, see The God Particle: If the Universe Is the Answer, What Is the Question?.
The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model (SM) of particle physics. The Higgs boson is an integral part of the theoretical Higgs mechanism. If shown to exist, it would help explain why other particles can have mass.[Note 1] It is the only elementary particle predicted by the Standard Model that has not yet been observed in particle physics experiments. Theories that do not need the Higgs boson also exist and would be considered if the existence of the Higgs boson were ruled out. They are described as Higgsless models.
If shown to exist, the Higgs mechanism would explain why the W and Z bosons, which mediate weak interactions, are massive whereas the related photon, which mediates electromagnetism, is massless. The Higgs boson is expected to be in a class of particles known as scalar bosons. (Bosons are particles with integer spin, and scalar bosons have spin 0.)
Experiments attempting to find the particle are currently being performed using the Large Hadron Collider (LHC) at CERN, and were performed at Fermilab's Tevatron until its closure in late 2011. Some theories suggest that any mechanism capable of generating the masses of elementary particles must become visible at energies above 1.4 TeV; therefore, the LHC (colliding two 3.5 TeV beams) is expected to be able to provide experimental evidence of the existence or non-existence of the Higgs boson.