Higgssector

The Higgs sector in particle physics refers to the part of the theory that contains scalar fields responsible for electroweak symmetry breaking and mass generation in the Standard Model. In the minimal Standard Model it consists of a single complex SU(2) doublet with hypercharge Y=1. The Higgs field acquires a vacuum expectation value v ≈ 246 GeV when the Higgs potential V(H) = μ^2 H†H + λ(H†H)^2 is minimized with μ^2 < 0. This spontaneous symmetry breaking gives masses to the W and Z gauge bosons via the Higgs mechanism, and fermions obtain mass through Yukawa couplings to the same field. The physical fluctuation around the vacuum is the Higgs boson, a CP-even scalar, with mass m_H = sqrt(2λ) v in the model.

Discovery and properties: In 2012, a Higgs-like particle with a mass near 125 GeV was observed by the ATLAS and CMS experiments at the Large Hadron Collider, confirming the basic mechanism of electroweak symmetry breaking. Measurements of production rates and decay channels indicate a scalar with spin 0 and CP-even character, whose couplings to gauge bosons and fermions are proportional to the respective particle masses, consistent with Standard Model predictions within current uncertainties. The observed decays include gamma gamma, ZZ, WW, bb, and tau tau, with a relatively narrow total width.

Beyond the Standard Model: The Higgs sector can be extended by adding additional scalar fields, such as second Higgs doublets (two-Higgs-doublet models), singlets, or triplets, and in supersymmetric theories like the MSSM. These extensions predict extra neutral or charged Higgs states and modify mixing angles and couplings. Experimental searches continue for non-SM scalars and for deviations in Higgs couplings to probe the structure and possible new physics of the Higgs sector.