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    Large Hadron Collider (LHC) and High-Luminosity LHC

    Also known as LHC, HL-LHC, HiLumi LHC, High-Luminosity LHC

    The Large Hadron Collider is CERN's 27 km superconducting ring near Geneva and the world's highest-energy collider, at 13.6 TeV; its ATLAS and CMS experiments discovered the Higgs boson in 2012.[1][2][3] It shut down on 27 June 2026 for a roughly four-year rebuild into the High-Luminosity LHC, which is due to start operating in 2030.[4][5]

    Editor reviewedUpdated Particle physics and cosmologyPhysicsScience
    Key facts

    What it is

    The Large Hadron Collider (LHC) is a 27-kilometre ring about 100 metres under the Franco-Swiss border near Geneva, run by CERN. It first started up on 10 September 2008.[1] About 9,000 superconducting magnets, cooled to 1.9 kelvin, steer two counter-rotating proton beams.[6] The beams collide at 13.6 TeV, the highest energy reached in a laboratory.[2] They cross at four points, home to the ATLAS, CMS, ALICE and LHCb detectors.[7]

    Main results

    On 4 July 2012 ATLAS and CMS announced the discovery of a particle consistent with the Higgs boson, the particle linked to the field that gives others mass.[3][8] In March 2025 LHCb reported the first observation of CP violation in baryon decays, a 2.45% matter-antimatter asymmetry in Lambda-b decays at 5.2 standard deviations.[9] CP violation of this kind is needed to explain why the universe contains matter but almost no antimatter.[10] Since its first collisions the LHC has delivered nearly 550 inverse femtobarns of data, almost twice its original target of 300.[11]

    Analysis of that data continues during the shutdown. At ICHEP 2026, CMS presented 28 new results, including an improved search for Higgs boson pair production that probes the Higgs self-coupling.[12] In September 2026 CERN reported that ATLAS and CMS had found the first strong evidence that pairs of Z bosons produced in Higgs decays are quantum entangled. This followed their earlier observation of entangled top quarks.[13] Smaller experiments also use the collider. FASER and SND@LHC detect neutrinos produced in LHC collisions.[14]

    End of Run 3 and Long Shutdown 3

    The final proton-proton collisions of Run 3 took place on 16 May 2026, and the final lead-lead collisions on 14 June. Beams circulated for the last time on 27 June.[4] The shutdown had been planned for earlier. In October 2024 CERN moved its start to July 2026 and the high-luminosity start to June 2030, mainly because the ATLAS and CMS Phase II detector upgrades had run into difficulties.[15]

    During Long Shutdown 3, 1.2 km of magnets and components in the LHC are being replaced. The accelerator complex is due to restart gradually from 2028.[5] In September 2026 teams began disconnecting the “inner triplet” focusing magnets on either side of ATLAS and CMS, which squeeze the beams just before they collide.[16] CERN says their niobium-tin replacements will reach 11.3 tesla, about 40% stronger than the current magnets. The first new quadrupole is due in the tunnel at the start of 2029, and 16 cryostats and 28 cryo-assemblies will be installed in all.[16] Some of the new magnets come from US national laboratories, as part of an exchange in which CERN supplies cryostats for the US-hosted DUNE.[17]

    The High-Luminosity LHC

    The High-Luminosity LHC (HL-LHC) is designed to raise the collider’s integrated luminosity tenfold beyond its original design value.[18] Its key technologies are:

    • niobium-tin quadrupole magnets, with fields 50% higher than the current magnets according to CERN’s technology page (a September 2026 CERN article gives about 40%)[16]
    • sixteen superconducting crab cavities next to ATLAS and CMS
    • magnesium-diboride superconducting links carrying more than 100,000 amperes.[19]

    CERN expects the HL-LHC to make at least 15 million Higgs bosons a year, against about three million from the LHC in 2017.[20] The 2026 European Strategy update calls completing the HL-LHC the highest medium-term priority, with operations extending to 2041.[21] CERN’s own 2026–2030 strategy names on-time completion of the machine and detectors its number-one priority.[22] The future-circular-collider is CERN’s preferred successor.[23]

    Questions readers ask

    When will the LHC run again?

    CERN's accelerator complex is due to restart gradually from 2028, and the High-Luminosity LHC is scheduled to begin operating in 2030.[5]

    What is changing in the High-Luminosity upgrade?

    About 1.2 km of the machine is being replaced. New niobium-tin magnets with 50% stronger fields and sixteen crab cavities are being installed next to ATLAS and CMS.[5][19]

    What has the LHC discovered?

    Its best-known discovery is the Higgs boson, announced by ATLAS and CMS in 2012. In 2025 LHCb also reported the first observation of matter-antimatter asymmetry in baryon decays.[3][9]

    How long will the High-Luminosity LHC run?

    The 2026 European Strategy update foresees operations extending to 2041.[21]

    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 Large Hadron Collider is a 27-kilometre ring about 100 metres underground on the Franco-Swiss border near Geneva; it first started up on 10 September 2008. confirmedas of 2026-10-10

    2. [2]

      The LHC collides protons at 13.6 TeV, the highest energy reached in a laboratory. confirmedas of 2026-10-10

    3. [3]

      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

    4. [4]

      Proton beams circulated in the LHC for the last time before Long Shutdown 3 on 27 June 2026; the final proton-proton collisions took place on 16 May and the final lead-lead collisions on 14 June. confirmedas of 2026-07-23

    5. [5]

      During Long Shutdown 3, 1.2 km of LHC magnets and components are being replaced; the accelerator complex is due to restart gradually from 2028 and the High-Luminosity LHC to begin operating in 2030. confirmedas of 2026-06-29

    6. [6]

      The LHC uses about 9,000 superconducting magnets cooled to 1.9 kelvin (-271 °C). confirmedas of 2026-10-10

    7. [7]

      The LHC's beams collide at four points, where the four main detectors ATLAS, CMS, ALICE and LHCb are located. confirmedas of 2026-10-10

    8. [8]

      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

    9. [9]

      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

    10. [10]

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

    11. [11]

      Since its first collisions the LHC has delivered nearly 550 inverse femtobarns of integrated luminosity, almost twice its original target of 300. confirmedas of 2026-07-23

    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]

      In September 2026 CERN reported that ATLAS and CMS had found strong evidence that pairs of Z bosons from Higgs boson decays are quantum entangled, the first such evidence for Z bosons, following their earlier observation of entangled top quarks. confirmedas of 2026-09-17

    14. [14]

      IceCube is a CERN Recognized Experiment, and CERN detects neutrinos produced at the LHC directly with its FASER and SND@LHC experiments. confirmedas of 2026-10-06

    15. [15]

      In October 2024 CERN moved the start of Long Shutdown 3 to July 2026 and the start of High-Luminosity LHC operation to June 2030, mainly because of difficulties with the ATLAS and CMS Phase II detector upgrades. confirmedas of 2024-10-04

    16. [16]

      In September 2026 CERN began disconnecting the LHC's inner-triplet focusing magnets on either side of ATLAS and CMS; their niobium-tin replacements produce 11.3-tesla fields, about 40% stronger, the first new quadrupole is due in the tunnel at the start of 2029, and 16 cryostats and 28 cryo-assemblies will be installed in total. confirmedas of 2026-09-17

    17. [17]

      CERN's Director-General said CERN is providing DUNE's two cryostats, while US national laboratories supply superconducting magnets for the High-Luminosity LHC; the CERN steel was scheduled to be moved underground in summer 2026. confirmedas of 2026-05-07

    18. [18]

      The High-Luminosity LHC is designed to increase the LHC's integrated luminosity by a factor of ten beyond its original design value. confirmedas of 2026-10-10

    19. [19]

      The HL-LHC upgrade installs niobium-tin quadrupole magnets with fields 50% higher than today's LHC magnets, sixteen crab cavities next to ATLAS and CMS, and magnesium-diboride superconducting links carrying more than 100,000 amperes. confirmedas of 2026-10-10

    20. [20]

      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

    21. [21]

      The 2026 European Strategy update keeps completing the High-Luminosity LHC as the highest medium-term priority, with operations extending to 2041. confirmedas of 2026-05-22

    22. [22]

      In September 2026 CERN published its 2026–2030 strategy, approved by the CERN Council in June, which makes timely completion of the High-Luminosity LHC its number-one priority and aims for CERN to be in a position to seek Council approval for FCC-ee in 2028. confirmedas of 2026-09-16

    23. [23]

      On 22 May 2026 the CERN Council updated the European Strategy for Particle Physics, naming the electron-positron Future Circular Collider as the preferred next flagship project. confirmedas of 2026-05-22

    Revision history (2)
    1. Page created.
    2. Added the September 2026 start of inner-triplet disconnection, Z-boson entanglement evidence, collider neutrino experiments, the CERN-US magnet exchange and CERN's 2026–2030 priority; noted CERN's two figures for the new magnets' field gain.

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

    Cite this page

    "Large Hadron Collider (LHC) and High-Luminosity LHC." ContentLora, updated Oct 10, 2026. https://contentlora.com/wiki/large-hadron-collider

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