Run 3 (LHC)

Run 3 (LHC)
Name	Run 3 (LHC)
Start	2022
End	2025
Location	CERN
Facility	Large Hadron Collider
Preceding	Run 2 (LHC)
Following	High-Luminosity Large Hadron Collider

Run 3 (LHC) Run 3 of the Large Hadron Collider at CERN was the third operational data-taking period for proton and heavy-ion collisions, following Run 1 (LHC) and Run 2 (LHC), aimed at higher energy, higher luminosity, and extended detector capability. The campaign involved collaborations among experiments such as ATLAS, CMS, ALICE, and LHCb, and engaged institutions including European Organization for Nuclear Research, Fermilab, DESY, SLAC National Accelerator Laboratory, and KEK. Run 3 interfaced with global programs at facilities like RHIC, J-PARC, IHEP Beijing, and TRIUMF to maximize synergies in heavy-ion physics, electroweak measurements, and beyond-Standard-Model searches.

Background and preparation

Preparatory work for Run 3 built on the discoveries and upgrades from Run 1 (LHC), Run 2 (LHC), and the Long Shutdown 2, involving planning committees including the CERN Council, the Particle Physics Community Planning Exercise, and coordination with the European Strategy for Particle Physics. Engineering and technical reviews incorporated lessons from projects at Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, Max Planck Society, Institut Laue–Langevin, and Paul Scherrer Institute, while funding and scheduling negotiations involved European Commission, National Science Foundation, Deutsche Forschungsgemeinschaft, UK Research and Innovation, and Agence Nationale de la Recherche. Safety and regulatory oversight referenced standards used by International Atomic Energy Agency and European Organization for Nuclear Research member states, with contributions from accelerator science groups at CERN Accelerator School, IHEP, and University of Oxford.

Machine upgrades and commissioning

The LHC lattice and subsystems underwent significant upgrades: new High Luminosity LHC prototypes influenced cryogenic and superconducting magnet developments, while the installation of crab cavities prototypes and improved Radio Frequency (RF) systems borrowed expertise from KEK and CERN accelerator divisions. Power converters and superconducting links were refurbished in collaboration with Siemens, Thales, Alstom, and national laboratories including CERN, Fermilab, and LBNL. Beam instrumentation upgrades referenced technology from Diamond Light Source, ESRF, SOLEIL, and DESY, with commissioning overseen by teams from CERN Beams Department, Max Planck Institute for Physics, and Imperial College London. Commissioning phases included dry runs coordinated with ATLAS, CMS, ALICE, and LHCb operations groups and technical coordination with Detector Control System experts from University of Manchester and ETH Zurich.

Beam parameters and operating performance

Run 3 targeted a center-of-mass energy increase for proton–proton collisions and higher instantaneous luminosity, informed by studies from John Adams Institute, Institute of High Energy Physics, and Petersburg Nuclear Physics Institute. Key beam parameters—bunch spacing, beam current, emittance, and beta*—were optimized using modelling tools from CERN Openlab, GEANT4 developers, and collaborators at University of California, Berkeley, Massachusetts Institute of Technology, University of Cambridge, University of Chicago, and Princeton University. Machine availability and integrated luminosity metrics were benchmarked against previous records set by Run 2 (LHC) and compared with projections by the European Strategy Group and High-Energy Physics Advisory Panel. Performance validation involved vacuum and cryogenic diagnostics used by Paul Scherrer Institute and beam loss monitoring schemes developed with Fermilab and SLAC.

Experimental program and detector upgrades

Experiment upgrades were extensive: ATLAS and CMS installed inner tracker replacements and timing layers developed with contributions from INFN, CEA, Max Planck Society, and KEK; LHCb upgraded its vertex locator and trigger system in partnerships with University of Barcelona, Nikhef, and University of Liverpool; ALICE implemented a new Inner Tracking System and time projection chamber improvements involving teams from Czech Technical University, Budker Institute of Nuclear Physics, and Niels Bohr Institute. Calorimetry, muon systems, and trigger/DAQ upgrades integrated electronics from STMicroelectronics, ON Semiconductor, and university groups at University of Tokyo, University of Melbourne, McGill University, and University of Geneva. The physics program encompassed precision measurements of the Higgs boson, searches for supersymmetry motivated by work at CERN Theory Department and Harvard University, flavour physics led by LHCb and Belle II, and heavy-ion collisions coordinated with ALICE and STAR.

Key physics results and milestones

Run 3 produced significant results: improved precision on Higgs boson couplings and rare decays, constraints on supersymmetry parameter space informed by analyses from ATLAS and CMS, and novel flavour anomalies investigated by LHCb with implications for models proposed at MIT, Caltech, and Institute for Advanced Study. Heavy-ion studies by ALICE yielded insights into quark–gluon plasma properties relevant to theoretical work from Princeton Institute for Advanced Study and Perimeter Institute, while electroweak measurements refined parameters of the Standard Model in collaboration with theorists at CERN Theory Department, NIKHEF, and INR RAS. Searches for dark matter and exotic resonances leveraged joint efforts with astroparticle groups at IceCube, Fermi Gamma-ray Space Telescope, Planck (spacecraft), and H.E.S.S..

Challenges, incidents, and mitigation measures

Operational challenges included beam-induced heating, vacuum issues, and magnet quenches; incident responses involved rapid interventions by CERN Safety Commission, CERN Fire Brigade, and technical teams from Siemens and Alstom. Radiation damage and aging electronics prompted replacement programs coordinated with ITER materials groups and semiconductor partners like Intel and STMicroelectronics. Data integrity and computing loads were managed by the Worldwide LHC Computing Grid, with capacity scaling through CERN Openlab, Google, Amazon Web Services, and national grid centers at GridPP, INFN-CNAF, NERSC, and DEISA. Community oversight and lessons learned were disseminated via conferences such as ICHEP, EPS-HEP, LHCP, and workshops at IPAC and CHEP.

Category:Large Hadron Collider runs