Brout–Englert–Higgs mechanism

Brout–Englert–Higgs mechanism
Name	Brout–Englert–Higgs mechanism
Caption	Schematic representation of a scalar field potential
Discoverers	Robert Brout, François Englert, Peter Higgs
Published	1964
Field	Particle physics
Related	Standard Model, Higgs boson, electroweak symmetry breaking

Brout–Englert–Higgs mechanism is the process by which gauge bosons and elementary fermions acquire mass via spontaneous symmetry breaking in the electroweak sector of the Standard Model. It introduces a scalar field whose nonzero vacuum expectation value breaks local gauge invariance, yielding a massive scalar excitation and giving longitudinal components to originally massless gauge fields. The mechanism underpins mass generation for the W and Z bosons and predicts the existence of the Higgs boson confirmed by collider experiments.

Introduction

The Brout–Englert–Higgs mechanism unifies ideas from theoretical work by Robert Brout, François Englert, and Peter Higgs with the electroweak theory developed by Sheldon Glashow, Steven Weinberg, and Abdus Salam. It operates within the framework of the Standard Model of particle physics, connecting to Quantum Electrodynamics via historical contributions from Paul Dirac and to Quantum Chromodynamics through structural parallels noted by Murray Gell-Mann. The mechanism played a pivotal role in the research programs at major laboratories such as CERN, Fermilab, and SLAC National Accelerator Laboratory, influencing initiatives by collaborations including ATLAS experiment and CMS experiment.

Theoretical Background

Theoretical foundations trace to spontaneous symmetry breaking concepts from condensed matter pioneers like Lev Landau, Pierre Curie, and John Bardeen, and field-theoretic treatments by Yoichiro Nambu and Jeffrey Goldstone culminating in the Goldstone theorem. Gauge theory formalism relies on work by Hermann Weyl, Yang Chen-Ning, Robert Mills, and extensions by Gerard 't Hooft and Martinus Veltman for renormalization. The electroweak model synthesizes contributions from Enrico Fermi's weak interaction phenomenology, Hideki Yukawa's meson theory, and experimental constraints established by groups at Brookhaven National Laboratory and DESY. Group-theoretic language uses representations of SU(2), U(1), and global symmetry analyses reminiscent of studies at Institute for Advanced Study and Princeton University.

Mechanism and Formalism

Formal description employs a complex scalar doublet in the fundamental representation of SU(2)×U(1), with Lagrangian terms inspired by prior field-theory work at University of Cambridge and Imperial College London. Spontaneous breaking of local gauge symmetry yields three would-be Nambu–Goldstone modes that are absorbed by the charged and neutral gauge bosons associated with generators analogous to those studied by Élie Cartan and Hermann Weyl, producing massive W± and Z0 fields as in formulations refined by Gerard 't Hooft and C. N. Yang. Gauge fixing and renormalization schemes build on procedures introduced by Ludvig Faddeev, Victor Popov, and Kenneth Wilson, and the perturbative calculations echo techniques from Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga. Fermion mass terms arise through Yukawa couplings, a mechanism extending concepts of Hideki Yukawa and implemented in model building at institutions like Massachusetts Institute of Technology and California Institute of Technology.

Experimental Confirmation

Experimental validation culminated at CERN with the discovery of a scalar resonance consistent with the predicted Higgs boson by the ATLAS experiment and the CMS experiment at the Large Hadron Collider, following decisive searches at LEP and Tevatron by collaborations such as ALEPH, DELPHI, OPAL, L3 and experiments at Fermilab including CDF Collaboration and DZero Collaboration. The statistical analysis techniques borrow from practices at Stanford Linear Accelerator Center and Lawrence Berkeley National Laboratory, and the detector technologies incorporate advances from Bell Labs and Brookhaven National Laboratory. Measurements of coupling strengths and decay channels involve comparisons to precision electroweak fits influenced by work from Ernest Moniz's contemporaries and global fits by groups at SLAC National Accelerator Laboratory and University of Chicago.

Extensions and Applications

Extensions include supersymmetric implementations advanced by Howard Georgi, Savas Dimopoulos, Sergio Ferrara, and Peter West in models like the Minimal Supersymmetric Standard Model, and composite Higgs scenarios investigated by researchers at CERN Theory Division and Perimeter Institute. Grand Unified Theory embeddings consider groups studied by Georgi and Glashow and later by Howard Georgi and Helen Quinn, with implications for baryogenesis explored by Andrei Sakharov. Cosmological applications connect to inflationary proposals by Alan Guth, Andrei Linde, and Paul Steinhardt, and to relic-density considerations addressed by teams at Harvard University and Princeton University. Beyond particle physics, analogues appear in condensed matter systems studied at Bell Labs and IBM Research, and in emergent phenomena examined at Max Planck Institute for Physics.

Historical Development

The conceptual arc began with symmetry and spontaneous breaking studies by Pierre Curie and Lev Landau, formalized in quantum field language by Yoichiro Nambu and later crystallized in three independent 1964 papers by Robert Brout, François Englert, and Peter Higgs, with contemporaneous clarifications by Gerald Guralnik, C. R. Hagen, and Tom Kibble. The electroweak unification achieved by Sheldon Glashow, Steven Weinberg, and Abdus Salam framed the mechanism's necessity, while renormalizability proofs by Gerard 't Hooft and Martinus Veltman established theoretical consistency. Experimental pursuit across decades involved facilities such as CERN, Fermilab, SLAC, and collaborations including ALEPH, ATLAS experiment, and CMS experiment, culminating in the 2012 announcement that transformed efforts at institutions like University of Oxford, University of Cambridge, University of California, Berkeley, and Imperial College London.

Category:Particle physics