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    How the Standard Model of particle physics works

    The Standard Model is the theory of the basic building blocks of matter: six quarks, six leptons and the particles that carry three of the four fundamental forces.[1][2] It has explained almost all experimental results since the 1970s, but it leaves out gravity, dark matter and neutrino masses, which is why physicists keep testing it.[3][4][5]

    Editor reviewedUpdated Particle physics and cosmologyPhysicsScience

    The building blocks

    Zoom into any piece of matter and you find atoms. Inside atoms are electrons and a nucleus made of protons and neutrons, and those are made of smaller particles called quarks. The Standard Model lists every known fundamental particle. There are six kinds of quark and six kinds of “lepton”, a family that includes the electron and the ghostly neutrinos.[1]

    The particles come in three “generations”. Each generation is a heavier copy of the one before. The muon, for example, is like an electron but about 200 times heavier.[1][6]

    The fermion content is three generations of quarks (up/down, charm/strange, top/bottom) and leptons (electron, muon and tau, each with a neutrino).[1] Developed in the early 1970s, the theory has explained almost all experimental results since.[3] Precision tests probe it through quantum loop effects. The muon’s magnetic anomaly, measured to 127 parts per billion at Fermilab, is the best-known example.[7]

    Forces and their carriers

    Nature has four fundamental forces: strong, weak, electromagnetic and gravitational. The Standard Model describes only the first three.[2] Each of the three works by exchanging a force-carrier particle, called a boson. Gluons carry the strong force, photons the electromagnetic force, and the W and Z bosons the weak force.[8] Gravity is left out because fitting it into the same framework has proved very hard.[2]

    The Higgs field

    Why do particles have mass at all? The Standard Model’s answer is an invisible field that fills the whole universe. Particles that interact with it strongly are heavy, and those that barely interact are light.[9] The field was proposed in 1964. On 4 July 2012 the ATLAS and CMS experiments at CERN’s large-hadron-collider announced they had found its particle, the Higgs boson.[9][10]

    Mass arises from coupling to the Higgs field (the Brout-Englert-Higgs mechanism) rather than being intrinsic.[9] Measuring the Higgs boson’s couplings, including to itself, is a central goal of the High-Luminosity LHC. That machine is expected to produce at least 15 million Higgs bosons a year.[11] At ICHEP 2026, CMS presented an improved search for Higgs pair production aimed at the self-coupling.[12] Proposed “Higgs factories” such as the electron-positron FCC are designed to study these interactions in detail.[13]

    The gaps

    The Standard Model is incomplete in at least four ways that experiments can test.

    1. Neutrino mass. Neutrinos change type as they travel, which proves they have mass. The model originally assumed they had none.[4] KATRIN’s 2025 limit puts the mass below 0.45 electronvolts, and DUNE will study how neutrinos and antineutrinos differ.[14][15]
    2. Dark matter. Ordinary matter is only about 5% of the universe’s content. Candidate dark matter particles come from theories beyond the Standard Model.[5][16]
    3. Matter and antimatter. CP violation, a difference in how matter and antimatter behave, is needed to explain why the universe is made of matter. In 2025 LHCb saw it for the first time in baryons, the family of particles that includes protons.[17][18]
    4. Gravity. It remains outside the theory.[2]

    Is the Standard Model in trouble?

    Not yet. The best-known recent anomaly, the muon’s magnetic moment, now agrees with an updated 2025 theory prediction.[19] However, two methods of calculating that prediction still disagree with each other by about three standard deviations.[20] The muon-g-2-experiment page has the details.

    Questions readers ask

    How many fundamental particles are in the Standard Model?

    Its matter particles are six quarks and six leptons, arranged in three generations. Forces are carried by bosons (gluons, photons, and the W and Z), and the Higgs boson completes the set.[1][8][10]

    Why is gravity not in the Standard Model?

    Fitting gravity into the Standard Model's framework has proved to be a difficult challenge, so the theory covers only the strong, weak and electromagnetic forces.[2]

    What does the Higgs boson do?

    Elementary particles get their mass by interacting with the Higgs field, which fills the universe. The Higgs boson is the particle associated with that field, discovered at CERN in 2012.[9][10]

    How heavy are neutrinos?

    Very light. The KATRIN experiment showed in 2025 that the neutrino mass is below 0.45 electronvolts.[14]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      The Standard Model's matter particles are six quarks and six leptons, each arranged in three generations; the leptons are the electron, muon, tau and their three neutrinos. confirmedas of 2026-10-10

    2. [2]

      Of the four fundamental forces (strong, weak, electromagnetic and gravitational), the Standard Model includes only the electromagnetic, strong and weak forces; gravity has proved difficult to fit into it. confirmedas of 2026-10-10

    3. [3]

      The Standard Model explains how the basic building blocks of matter interact; it was developed in the early 1970s and has explained almost all experimental results since. confirmedas of 2026-10-10

    4. [4]

      Neutrinos change flavour (electron, muon, tau) as they travel, which proves they have mass; the Standard Model originally assumed neutrinos were massless. confirmedas of 2026-10-10

    5. [5]

      According to CERN, ordinary matter makes up about 5% of the universe's content, dark matter about 27% and dark energy about 68%. confirmedas of 2026-10-10

    6. [6]

      Muons are particles similar to electrons but about 200 times more massive. confirmedas of 2025-06-03

    7. [7]

      On 3 June 2025 Fermilab's Muon g-2 experiment released its final measurement of the muon's magnetic anomaly, with a precision of 127 parts per billion, better than its 140 ppb design goal. confirmedas of 2025-06-03

    8. [8]

      In the Standard Model, three forces result from exchanging force-carrier particles called bosons; gluons carry the strong force, photons the electromagnetic force, and W and Z bosons the weak force. confirmedas of 2026-10-10

    9. [9]

      Elementary particles get their mass by interacting with the Higgs field, which was proposed in 1964 and fills the universe. confirmedas of 2026-10-10

    10. [10]

      On 4 July 2012 the ATLAS and CMS collaborations at CERN announced the discovery of a new particle consistent with the Higgs boson. confirmedas of 2026-10-10

    11. [11]

      CERN expects the High-Luminosity LHC to produce at least 15 million Higgs bosons a year, compared with about three million from the LHC in 2017. confirmedas of 2026-10-10

    12. [12]

      At the ICHEP 2026 conference in Natal, Brazil (30 July to 5 August 2026), CMS presented 28 new results, including an improved search for Higgs boson pair production that advances sensitivity to the Higgs self-coupling. confirmedas of 2026-08-05

    13. [13]

      CERN describes the FCC as a Higgs factory designed to study the Higgs boson and its interactions in detail, and to search for dark matter candidates and other physics beyond the Standard Model. confirmedas of 2026-10-10

    14. [14]

      In April 2025 the KATRIN experiment reported in Science that the neutrino mass is below 0.45 electronvolts (90% confidence), half the previous limit, using 259 days of data from 2019 to 2021 and more than 36 million electrons. confirmedas of 2025-04-16

    15. [15]

      DUNE's main goals are to study differences between neutrinos and antineutrinos that could explain why the universe contains matter, to search for physics beyond the Standard Model, and to detect neutrinos from supernovae. confirmedas of 2026-10-10

    16. [16]

      Hypothesised particles from theories beyond the Standard Model, such as supersymmetric partners of known particles, are among the proposed dark matter candidates. confirmedas of 2026-10-10

    17. [17]

      CP violation is needed to explain why today's universe contains matter with essentially no leftover antimatter. confirmedas of 2025-03-25

    18. [18]

      In March 2025 LHCb reported the first observation of matter-antimatter (CP) violation in baryon decays, a 2.45% asymmetry in Lambda-b baryon decays with 5.2 standard deviations significance, using LHC Run 1 and 2 data. confirmedas of 2025-03-25

    19. [19]

      The Muon g-2 Theory Initiative's 2025 Standard Model prediction differs from the experimental average by 38 plus or minus 63 (×10⁻¹¹), showing no significant tension between theory and experiment. confirmedas of 2025-05-27

    20. [20]

      The Theory Initiative's 2020 data-driven prediction and its 2025 lattice-QCD-based prediction disagree at the level of about three standard deviations, leaving open whether a sign of new physics exists. confirmedas of 2025-07-08

    Revision history (1)
    1. Page created.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "How the Standard Model of particle physics works." ContentLora, updated Oct 10, 2026. https://contentlora.com/explain/how-the-standard-model-works

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