The Higgs Boson Discovery

The Standard Model's last missing piece

First published: ATLAS Collaboration, "Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC", *Phys. Lett. B* 716 (2012): 1–29; CMS Collaboration, ibid. 30–61.

Two LHC detectors independently observe a new boson at ~125 GeV — the predicted Higgs particle that completes the Standard Model.

The Standard Model of particle physics, as formulated in the 1960s and 1970s, required a mechanism to give masses to the W and Z bosons (and ultimately to fermions) while preserving local gauge symmetry. Higgs, Brout-Englert, and others (1964) proposed an all-pervading scalar field whose spontaneous symmetry breaking gave masses through coupling strength. The associated boson was the last unconfirmed prediction of the Standard Model. After decades of search at colliders of increasing energy, the LHC's ATLAS and CMS detectors independently observed in July 2012 a new neutral boson at approximately 125 GeV, with decay channels consistent with Standard Model predictions. The discovery completed the SM as the empirical theory of particle physics up to current energies, vindicated the gauge-symmetry-breaking mechanism as the origin of mass for fundamental particles, and was recognised with the 2013 Nobel Prize for Englert and Higgs.