LHC

LHC
Name	Large Hadron Collider
Caption	A section of the circular tunnel housing the accelerator.
Location	Geneva
Coordinates	46, 14, 06, N...
Institution	CERN
Type	Synchrotron
Beam type	Protons, Lead ions
Target	Fixed target
Energy	6.8 TeV per beam (13.6 TeV collision energy)
Circumference	26,659 m
Website	https://home.cern/science/accelerators/large-hadron-collider

LHC. It is the world's largest and highest-energy particle accelerator, situated in a 26.7-kilometer circular tunnel beneath the border of Switzerland and France. Operated by the European Organization for Nuclear Research, its primary purpose is to collide hadrons—typically protons or lead ions—at velocities approaching the speed of light to probe the fundamental structure of matter. The immense collision energies allow physicists to test predictions of the Standard Model, search for new particles, and explore conditions similar to those just after the Big Bang.

Overview

The facility was constructed by CERN between 1998 and 2008, utilizing the pre-existing tunnel of the Large Electron–Positron Collider. It is an international scientific endeavor involving thousands of scientists, engineers, and technicians from hundreds of universities and research institutes globally. The accelerator complex functions as the final stage in a chain of pre-accelerators, including the Proton Synchrotron and the Super Proton Synchrotron, which progressively boost particle energies before injection. Research at the facility is conducted by several major international collaborations, each operating a dedicated particle detector positioned at key interaction points around the ring.

Design and components

The machine consists primarily of a ring of 1,232 superconducting dipole magnets cooled by liquid helium to 1.9 kelvin, which bend and focus the particle beams. An additional 392 quadrupole magnets are used for beam focusing. Two separate beam pipes within a common cryostat maintain counter-rotating beams, which are brought into collision at four designated interaction points. Critical systems include a massive cryogenics infrastructure, ultra-high vacuum systems within the beam pipes, and sophisticated radio frequency cavities that provide acceleration. The entire system is monitored and controlled from the CERN Control Centre, with data distributed worldwide via the LHC Computing Grid.

Operational history

First beams were circulated successfully in September 2008, but an initial malfunction in the superconducting magnet electrical system caused a significant delay. Collisions at a record energy of 3.5 TeV per beam commenced in 2010, beginning the first long physics run. The machine operated at 4 TeV per beam in 2012, a pivotal year for discoveries. After its first run, it underwent a major shutdown for consolidation and upgrades. Operations resumed in 2015 at the higher design energy of 6.5 TeV per beam, later increased to 6.8 TeV. Its operational schedule is defined by multi-year "runs" interspersed with longer "Long Shutdown" periods for maintenance and upgrades.

Major experiments

Four main detector collaborations conduct research at the collision points. The ATLAS experiment and the CMS experiment are large, general-purpose detectors designed to investigate a wide range of physics, including the search for the Higgs boson and supersymmetry. The ALICE experiment is specialized to study the properties of the quark–gluon plasma created in heavy-ion collisions. The LHCb experiment is focused on precision measurements of CP violation and the behavior of bottom quarks to understand the matter-antimatter asymmetry of the universe. Smaller experiments like TOTEM and LHCf also occupy dedicated interaction regions.

Scientific achievements and discoveries

The most celebrated achievement was the joint discovery of a new particle consistent with the Higgs boson by the ATLAS and CMS collaborations in July 2012, a feat for which theorists François Englert and Peter Higgs were awarded the Nobel Prize in Physics in 2013. The machine has since made precise measurements of the boson's properties. Other significant results include extensive tests of the Standard Model, stringent constraints on potential supersymmetric particles, and detailed studies of quark–gluon plasma by ALICE. It has also ruled out the existence of numerous predicted particles and phenomena, such as certain types of leptoquarks, guiding theoretical physics.

Future upgrades

A major upgrade program is underway to significantly increase the number of particle collisions, known as luminosity. The ongoing High Luminosity LHC project aims to install new, more powerful superconducting magnets, advanced cryogenics, and upgraded interaction regions around 2029. This will increase the integrated luminosity by a factor of ten, enabling the collection of vastly more data to study rare processes with greater precision. These upgrades are essential for detailed study of the Higgs boson and for enhancing sensitivity to potential new physics beyond the Standard Model, ensuring the facility's research output for decades.

Category:Particle accelerators Category:CERN Category:Buildings and structures in the canton of Geneva Category:Research facilities in Switzerland