The Higgs boson is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. It is the only Standard Model particle not yet observed, but plays a key role in explaining the origins of the mass of other elementary particles, in particular the difference between the massless photon and the relatively heavy W and Z bosons. Elementary particle masses, and the differences between electromagnetism (caused by the photon) and the weak force (caused by the W and Z bosons), are critical to many aspects of the structure of microscopic (and hence macroscopic) matter; thus, if it exists, the Higgs boson has an enormous effect on the world around us.
As of 2007, no experiment has directly detected the existence of the Higgs boson, but there is indirect evidence for it. The Higgs mechanism, which gives mass to vector bosons, was first theorized in 1964 by Peter Higgs, François Englert and Robert Brout, working from the ideas of Philip Anderson, and independently by G. S. Guralnik, C.R. Hagen, and T. W. B. Kibble . Steven Weinberg and Abdus Salam were the first to apply the Higgs mechanism to the electroweak symmetry breaking. The electroweak theory predicts a neutral particle whose mass is not far from the W and Z bosons.

Theoretical overview
As of 2007, the Higgs boson has not been observed experimentally, despite large efforts invested in accelerator experiments at CERN and Fermilab. The non-observation of clear signals leads to an experimental lower bound for the Higgs boson mass of 114.4 GeV at 95% confidence level. A small number of events were recorded by experiments at LEP collider at CERN that could be interpreted as resulting from Higgs bosons, but the evidence is inconclusive. but no evidence is yet compelling enough to convince the scientific community as a whole.
As of August of 2007, Tevatron results continue to hint at a Higgs mass near the low end of the allowed range, presenting a potentially awkward situation to the LHC project.

Experimental search

Main article: Higgsless model Alternatives to the Higgs mechanism for electroweak symmetry breaking

Main article: Higgs boson (fiction)