| Higgs boson | |
|---|---|
| Name | Higgs boson |
| Composition | elementary particle |
| Statistics | Boson |
| Group | Scalar boson |
| Discovered | 4 July 2012 |
| Discovered at | Large Hadron Collider (ATLAS and CMS) |
| Theorists | Peter Higgs, François Englert, Robert Brout, Gerald Guralnik, C. R. Hagen, Tom Kibble |
| Mass | ~125 GeV/c^2 |
Higgs boson
The Higgs boson is an elementary scalar particle associated with the Higgs field whose nonzero vacuum expectation value gives mass to elementary particles via the Higgs mechanism. It occupies a central place in quantum field theory and the Standard Model, and its discovery confirmed a key element of modern particle physics while informing questions in cosmology and beyond-Standard-Model searches.
The Higgs boson provides the observable excitation of the Higgs field, an essential component in the electroweak sector that reconciles gauge symmetry with nonzero fermion and gauge boson masses. In Quantum Physics contexts, the particle illustrates how spontaneous symmetry breaking in a relativistic quantum field generates mass terms without violating local gauge symmetry. Its existence underpins precision tests at colliders such as the Large Hadron Collider and informs theoretical frameworks including quantum electrodynamics, quantum chromodynamics, and unified theories pursued at institutions like CERN and major universities.
The theoretical development began in the 1960s with papers by Peter Higgs, François Englert, and Robert Brout and contemporaries Gerald Guralnik, C. R. Hagen, and Tom Kibble, which applied spontaneous symmetry breaking to relativistic gauge theories. The Higgs mechanism describes how a scalar field with a Mexican hat potential acquires a nonzero vacuum expectation value, yielding mass terms for the W boson and Z boson while leaving the photon massless. This preserves gauge invariance at the Lagrangian level and integrates with the Glashow–Weinberg–Salam model of electroweak unification. The mechanism is formalized in the language of Lagrangians and perturbation theory, and it motivated searches for a physical scalar particle—the Higgs boson—whose properties follow from the shape of the potential and coupling assignments.
The Standard Model predicts a single, neutral, CP-even scalar with no internal quantum numbers beyond mass and spin 0. Predicted decay channels and branching ratios—such as H→γγ, H→ZZ*→4ℓ, H→WW*→ℓνℓν, H→bb̄, and H→τ+τ−—guided experimental strategies. The Higgs couples proportionally to particle masses, giving heavier fermions and massive gauge bosons larger partial widths; this mass-proportional coupling is a hallmark distinguishing the Higgs from other resonances. Precision measurements of the Higgs mass (~125 GeV/c^2), total width, spin-parity, and production modes (gluon fusion, vector boson fusion, associated production with top quark or W/Z bosons) are critical to confirm the Standard Model and to search for deviations signaling new physics like supersymmetry, composite Higgs models, or extra dimensions.
Large-scale experimental confirmation came from the ATLAS experiment and CMS experiment at the Large Hadron Collider at CERN on 4 July 2012, following earlier constraints from the Large Electron–Positron Collider (LEP) and the Tevatron at Fermilab. The discovery used high-luminosity proton–proton collisions at 7–8 TeV to observe excesses in diphoton and four-lepton channels consistent with a Standard Model Higgs. Subsequent runs at 13 TeV improved measurements of couplings, spin-parity (confirming 0+), and rare decays. International collaborations, national laboratories, and funding agencies—such as CERN, Fermilab, DESY, and national science foundations—coordinated detector upgrades and data analysis leading to Nobel Prizes awarded to principal theorists.
Within the Standard Model the Higgs boson completes the particle roster and provides mass generation for fermions via Yukawa couplings and for electroweak gauge bosons via symmetry breaking. However, several outstanding puzzles motivate extensions: the hierarchy (naturalness) problem concerning quadratically divergent corrections to the Higgs mass; the absence of a Standard Model candidate for dark matter; and the matter–antimatter asymmetry implicating electroweak baryogenesis scenarios requiring beyond-Standard-Model Higgs sectors. Proposed extensions include supersymmetry (predicting multiple Higgs bosons), two-Higgs-doublet models, and strongly coupled or composite Higgs frameworks inspired by technicolor-like dynamics. Precision Higgs studies serve as a window into high-scale physics and guide proposals for next-generation facilities such as the International Linear Collider or future circular colliders.
The Higgs field's role in the early universe affects phase transitions, inflationary model-building, and the stability of the electroweak vacuum. The measured Higgs and top quark masses inform vacuum stability analyses, with implications for whether the current vacuum is absolutely stable, metastable, or near-critical over cosmological timescales. Interactions between the Higgs sector and hypothetical fields could influence reheating, baryogenesis, and dark sector couplings relevant to astroparticle physics experiments. Consequently, Higgs physics sits at the nexus of particle physics, cosmology, and national-scale scientific programs preserving technological leadership and collaborative institutions that sustain long-term basic research.
Category:Elementary particles Category:Standard Model