CERN Large Hadron Collider

CERN Large Hadron Collider
Name	Large Hadron Collider
Caption	The Compact Muon Solenoid during installation at the Large Hadron Collider
Location	Meyrin, Geneva
Coordinates	46.233, 6.055
Established	2008
Operator	CERN
Type	Particle accelerator
Length	27 km
Energy	6.5 TeV per beam (2015–2018)

Contents

CERN Large Hadron Collider The Large Hadron Collider is a circular particle accelerator and collider built and operated by CERN near Geneva on the France–Switzerland border. It was designed to probe high-energy particle physics phenomena, test predictions of the Standard Model, and search for new particles and forces, evolving experimental programs such as ATLAS, CMS, ALICE and LHCb. The project links major laboratories and universities including Fermilab, SLAC, DESY, KEK, INFN, and collaborations with the Max Planck Society, Imperial College London, University of Oxford, Harvard University, and Princeton University.

Overview and purpose

The facility consists of a 27-kilometre ring of superconducting magnets and accelerating structures near Franco-Swiss border installations such as Meyrin and Saint-Genis-Pouilly, serving experiments like ATLAS experiment, CMS experiment, ALICE experiment, and LHCb experiment. Its purpose is to collide protons and heavy ions to investigate phenomena predicted by the Standard Model, test theories including supersymmetry, extra dimensions, and search for particles like the Higgs boson, dark matter candidates and exotic resonances, while providing precision measurements relevant to quantum chromodynamics, electroweak interaction, and CP violation. The LHC's outcomes have implications for institutions such as the European Space Agency, National Aeronautics and Space Administration, UNESCO, and national research agencies including UK Research and Innovation, Agence Nationale de la Recherche, and Deutsche Forschungsgemeinschaft.

Conceived at CERN as a successor to the Super Proton Synchrotron and Large Electron–Positron Collider, the LHC project involved design work by teams from CERN, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, University of Geneva, ETH Zurich, Université de Paris, Uppsala University, and University of Cambridge. Key milestones include approval by CERN Council, groundbreaking in the 1990s, magnet and cryostat development collaborating with ANSALDO, Siemens, Thales Group, and Alstom, and component testing at facilities like European XFEL and ISOLDE. Construction faced technical challenges similar to those at Tevatron, overcoming magnet quench incidents and the 2008 initial cryogenic failure, followed by recovery efforts led by Rolf-Dieter Heuer and directors including Lyn Evans and Fabiola Gianotti. Funding and governance involved members such as France, Germany, United Kingdom, Italy, United States Department of Energy, and agencies like European Investment Bank.

The accelerator complex includes injector chains starting with Linear Accelerator 2 (Linac2), Proton Synchrotron Booster, Proton Synchrotron, and Super Proton Synchrotron feeding the main ring. The superconducting dipole magnets, developed with contributions from Alstom, Siemens, and laboratories like CERN and FZ Jülich, operate at 1.9 K using helium refrigeration systems similar to Large Helical Device technology. Radio-frequency acceleration uses klystron systems and superconducting radio frequency cavities; beam focusing relies on quadrupole magnets and collimation systems tested at Brookhaven National Laboratory and DESY. Design parameters include a 27 km circumference tunnel originally excavated using technology from projects such as Channel Tunnel and similar tunnelling techniques applied by contractors like Balfour Beatty and Alstom. Key detectors—ATLAS experiment, CMS experiment, ALICE experiment, LHCb experiment—incorporate subdetectors inspired by work at UA1 experiment, UA2 experiment, CERN ISR, and detector technologies from CALICE, RD50, RD51, GEANT4 simulations, and sensor development at CERN microelectronics group and INFN.

Operation cycles include runs managed by CERN's Beams Department coordinating with experiment collaborations led by spokespersons from institutions such as University of Manchester, RWTH Aachen University, Sorbonne University, University of Tokyo, and University of California, Berkeley. Major experiments—ATLAS experiment (general-purpose), CMS experiment (general-purpose), ALICE experiment (heavy-ion), LHCb experiment (flavor physics)—are supplemented by smaller projects like TOTEM experiment, LHCf experiment, MoEDAL experiment, and fixed-target initiatives involving NA61/SHINE. Data acquisition uses distributed computing through the Worldwide LHC Computing Grid supported by CERN OpenLab, European Grid Infrastructure, Fermilab, NIKHEF, TRIUMF, and national centres like GRIDKA. Operations coordinate with safety and cryogenics teams, beam commissioning experts from SLAC and Fermilab, and software development groups using tools from ROOT and Gaudi.

The LHC enabled the discovery of the Higgs boson with results announced by ATLAS collaboration and CMS collaboration in 2012, confirming mechanisms proposed by Peter Higgs, François Englert, and Robert Brout. Precision measurements of electroweak parameters have constrained models like supersymmetry and theories involving extra dimensions such as the Randall–Sundrum model and ADD model. Heavy-ion collisions studied by ALICE experiment shed light on quark–gluon plasma properties relevant to early-universe conditions modeled in Big Bang theory simulations. Flavor physics from LHCb experiment produced measurements of CP violation building on work from NA48 experiment and BaBar, with implications for matter–antimatter asymmetry studies. Results have influenced theoretical frameworks at institutes like Perimeter Institute, Institute for Advanced Study, and collaborations with NASA astrophysics missions searching for dark matter signals.

Safety oversight involves CERN's safety groups, national regulators including Swiss Federal Office of Public Health and French Nuclear Safety Authority, and international reviews by panels with experts from IAEA, European Commission, and universities such as Université de Genève and ETH Zurich. Environmental management addresses cryogenics, helium procurement linked to global supplies involving companies like Air Liquide, and energy consumption coordinated with regional grids managed by RTE (Réseau de Transport d'Électricité), Swissgrid, and policies from European Union. Societal impacts include technology transfer to industry partners like Thales Group and Siemens, medical imaging advances influencing Institut Curie and Mayo Clinic through detector innovations, education and outreach via CERN Summer Student Programme, collaborations with museums like the Science Museum (London), and public engagement during major results announced by figures such as Fabiola Gianotti and Rolf-Dieter Heuer. The project stimulated regional economies of Geneva, Vaud, Ain (department), and cross-border scientific diplomacy among member states including France, Switzerland, Italy, Germany, and United Kingdom.