The Higgs boson was found in 2012 — and confirmed in 2013

The Higgs boson was announced at CERN on 4 July 2012, when the ATLAS and CMS experiments at the Large Hadron Collider reported a new particle with a mass of about 125 GeV, the particle predicted in 1964. Strictly, that day’s claim was a new boson consistent with the Higgs; physicists concluded it was a Higgs boson in March 2013, after analysing about two and a half times more data and checking its spin.

Both teams reported signals at the 5-sigma level, the threshold particle physicists treat as a discovery. For CMS, that meant the probability of ordinary background fluctuating up to fake the bump was about one in three million. The search was hard because the Higgs appears in only about one in a billion LHC collisions and decays almost instantly, so it has to be spotted through the particles it turns into. To avoid fooling themselves, CMS analysed its 2012 data “blind”, not looking at the region of interest until its selection criteria were fixed.

A common shorthand says the Higgs “gives everything its mass”. It gives elementary particles such as electrons and quarks their mass: the more strongly a particle interacts with the Higgs field, the heavier it is, and photons, which ignore it, stay massless.

But most of the mass of you and everything made of protons and neutrons does not come from the Higgs. The three quarks at a proton’s core supply only a small fraction of its mass; the rest emerges from quark motion and the strong force carried by gluons.

Peter Higgs and François Englert shared the 2013 Nobel Prize in Physics for the theory. Since then, experiments have measured the boson’s interactions with tau leptons (2016) and with top and bottom quarks (2018), testing whether it behaves exactly as the Standard Model predicts.