The search for the Standard Model Higgs boson at ALEPH

The standard model of elementary particles is a remarkably successful theory. The Higgs boson, the particle responsible for giving masses to those particles with mass, is the only particle in the standard model which has not been experimentally observed. In data collected in 2000 at the Large Electron-Positron Collider, at center of mass energies up to 209 GeV, an excess of Higgs-like events was observed. This excess is consistent with the production of a Higgs boson with invariant mass 115.6 ± 0.8 GeV/c 2. The effect is dominated by an excess in the four-jet channels in ALEPH caused by three high purity signal candidates.