2013 Nobel Prize in Physics
Reason for Award
For the theoretical discovery of the Brout–Englert–Higgs mechanism, proposed in 1964, which explains how elementary particles acquire mass and was later confirmed by the observation of the Higgs boson by the ATLAS and CMS experiments at CERN’s Large Hadron Collider. The award cites the seminal papers Phys. Rev. Lett. 13 (1964) 321 (Englert & Brout), Phys. Rev. Lett. 13 (1964) 508 (Higgs), and Phys. Rev. 145 (1966) 1156 (Higgs).
Laureates
Belgium
United Kingdom of Great Britain and Northern Ireland
Explanation
Everything around us is made of tiny particles. These particles have weight (mass), letting an apple stay on a table. Long ago scientists did not know where this mass came from. François Englert and Peter Higgs suggested that an invisible “Higgs ocean” fills all space and gives mass to particles that move through it. In 2012 a ripple of this ocean—the Higgs boson—was found at CERN, proving their idea.
Related Keywords
Higgs boson
The Higgs boson is the quantum excitation of the Higgs field and a scalar particle. In 2012 the ATLAS and CMS experiments at CERN discovered a candidate with a mass of about 125 GeV/c². Because it is spin-0 and electrically neutral, measuring its decay patterns and quantum numbers is crucial to confirm its identity. The Standard Model predicts that its coupling strengths are proportional to the masses of other particles. Precision studies of these couplings offer a sensitive probe for physics beyond the Standard Model.
origin of mass
The masses of elementary particles cannot be explained by simply weighing them. Fermion masses arise through Yukawa interactions with the Higgs field, while gauge-boson masses come from the Higgs vacuum expectation value. Most of the mass of nucleons, however, originates from QCD binding energy, showing that mass has multiple sources. The BEH mechanism provides a unified description of mass generation in the electroweak sector. Understanding the origin of mass is fundamental to grasping the universe’s history and the stability of matter.
Standard Model of particle physics
The Standard Model unifies the strong, weak and electromagnetic forces in a gauge-theory framework. It is based on the symmetry group SU(3)_C×SU(2)_L×U(1)_Y and contains 17 known fundamental particles. The BEH mechanism breaks electroweak symmetry, giving mass to W, Z bosons and fermions, thereby completing the model. Gravity, dark matter and neutrino masses remain outside its scope as open questions. Accelerator experiments have tested the Standard Model’s predictions with high precision for decades.
spontaneous symmetry breaking
Spontaneous symmetry breaking occurs when the ground state of a system does not share the symmetry of its governing equations. It is a universal mechanism seen in ferromagnets, crystals and many other systems. In the BEH mechanism the Higgs field acquires a non-zero vacuum expectation value, breaking electroweak symmetry. Massless Goldstone modes predicted by the Nambu–Goldstone theorem are absorbed by gauge bosons, giving them mass. The concept is pivotal for understanding early-universe phase transitions and new phases of matter.
Brout–Englert–Higgs mechanism
The Brout–Englert–Higgs (BEH) mechanism, proposed independently in 1964, explains how gauge fields acquire mass. A scalar field with a Mexican-hat potential gains a vacuum expectation value, leaving gauge symmetry hidden yet intact. The resulting Goldstone modes are absorbed by gauge bosons, providing the longitudinal components that give W and Z their masses. The remaining scalar degree of freedom emerges as the Higgs boson, whose discovery was essential to test the theory. The mechanism preserves unitarity at high energies and ensures renormalizability.
Large Hadron Collider (LHC)
The LHC is a 27-km circular accelerator built underground on the French-Swiss border. It collides protons or lead ions at center-of-mass energies up to 14 TeV. Detectors such as ATLAS and CMS record tens of millions of collision events every second. Data from Run 1 (2010–2012) led to the discovery of the Higgs boson. A forthcoming high-luminosity upgrade will increase statistics ten-fold and enhance sensitivity to rare processes.
ATLAS experiment
ATLAS is a 46-meter-long, 7,000-tonne general-purpose detector and a flagship experiment at the LHC. Layered silicon trackers, calorimeters and muon chambers reconstruct particles with high precision. In the Higgs discovery ATLAS provided decisive evidence in the γγ and ZZ*→4ℓ channels. A fast trigger system reduces a billion collisions per second to a few hundred thousand for further processing. ATLAS also leads searches for new particles and dark-matter candidates.
CMS experiment
CMS is built around a powerful superconducting solenoid magnet and weighs about 14,000 tonnes. Its 3.8-Tesla field, high-resolution silicon pixel detector and crystal calorimeter make it excellent at measuring photons and electrons. During the Higgs discovery CMS independently confirmed the signal seen by ATLAS, increasing statistical significance. The experiment continues to perform precision measurements and searches for new physics. In the high-luminosity LHC era, vastly increased data will allow detailed study of rare decays.
gauge symmetry
Gauge symmetry demands that a field theory remain invariant under local phase transformations. This principle introduces conserved quantities such as electric and color charge and predicts gauge bosons that mediate interactions. Explicit mass terms break the symmetry, forcing gauge bosons to be massless. The BEH mechanism employs spontaneous symmetry breaking to retain gauge symmetry while giving gauge bosons effective mass. Gauge symmetry also guarantees renormalizability, ensuring theoretical consistency.
electroweak interaction
At high energies the electromagnetic and weak forces merge into a single electroweak force. The combined gauge group SU(2)_L×U(1)_Y provides the mathematical framework. When the Higgs field acquires a vacuum expectation value the symmetry breaks, leaving the photon massless while W and Z bosons become heavy. Electroweak theory accurately predicts observables such as W and Z masses and the weak mixing angle. Precision electroweak tests are a key indirect probe of new physics.