The electroweak unification appears mainly in the neutral current processes. The transition probabilities of all of them are predicted in terms of the weak mixing angle. Measuring the weak mixing angle.

Theory predicts the existence of three vector bosons, W+, W− and Z0. It does not predict their masses, but precisely states how they are related with two measured quantities: the Fermi constant and the weak mixing angle. The UA1 experiment and the discovery of the vector bosons.

The precision tests of the electroweak theory performed at the LEP electron–positron collider and at the Tevatron proton–antiproton collider.

The last missing element of the SM, the Higgs boson. The spontaneous symmetry breaking and the boson. The searches at LEP and at the Tevatron. The Large Hadron Collider and the ATLAS and CMS experiments. The discovery of 2012. Checking Higgs physics, measuring its mass and width, its spin and parity, its couplings to the bosons and to the fermions. All agree with the predictions of the Standard Model, so completing the experimental verification of its basic building blocks.

This chapter explains how we can reconcile massive particles within a gauge symmetry. The notion of spontaneous symmetry breaking is introduced, first in a simple model and then with the gauge group of the Standard Model. The Brout–Englert–Higgs mechanism is then presented in detail. The rest of the chapter is devoted to the experimental discovery of the Higgs boson and its properties with the most up-to-date experimental measurements.