StandardmodellLagrange

StandardmodellLagrange, more commonly called the Standard Model Lagrangian, is the quantum field theory that describes the behavior and interactions of the fundamental particles of the Standard Model. It encodes the dynamics of quarks, leptons, gauge bosons, and the Higgs field under the gauge symmetry SU(3)×SU(2)×U(1), and it excludes gravity. The Lagrangian specifies how quarks and leptons interact via gauge bosons—the gluons of the strong force, the W and Z bosons of the weak force, and the photon of electromagnetism. A complex scalar Higgs field provides spontaneous electroweak symmetry breaking and, through Yukawa couplings, endows fermions with mass.

The structure includes kinetic terms for gauge fields and fermions, implemented with covariant derivatives that encode gauge interactions; Yukawa interaction terms between fermions and the Higgs field that generate fermion masses after symmetry breaking; and the Higgs potential responsible for the nonzero vacuum expectation value. The resulting spectrum contains massless photons and gluons, massive W and Z bosons, and fermions with masses proportional to their Yukawa couplings, along with a scalar Higgs boson.

The Standard Model Lagrangian is renormalizable and has withstood extensive experimental tests, including precision electroweak measurements and the discovery of the Higgs boson. Nevertheless, it does not explain phenomena such as neutrino masses in its minimal form, dark matter, or gravity, and physicists explore extensions and effective theories beyond the Standard Model.