Seven experiments at the Large Hadron Collider (LHC) use detectors to analyse the myriad of particles produced by collisions in the accelerator. These experiments are run by collaborations of scientists from institutes all over the world. Each experiment is distinct, and characterized by its detectors.
The biggest of these experiments, ATLAS and CMS, use general-purpose detectors to investigate the largest range of physics possible. Having two independently designed detectors is vital for cross-confirmation of any new discoveries made. ALICE and LHCb have detectors specialized for focussing on specific phenomena. These four detectors sit underground in huge caverns on the LHC ring.
The smallest experiments on the LHC are TOTEM and LHCf, which focus on "forward particles" – protons or heavy ions that brush past each other rather than meeting head on when the beams collide. TOTEM uses detectors positioned on either side of the CMS interaction point, while LHCf is made up of two detectors which sit along the LHC beamline, at 140 metres either side of the ATLAS collision point. MoEDAL uses detectors deployed near LHCb to search for a hypothetical particle called the magnetic monopole.
While the main focus of research at CERN has moved in recent years towards the LHC, experiments at other accelerators and facilities both on-site and off remain an important part of the laboratory’s activities.
In “fixed-target” experiments, a beam of accelerated particles is directed at a solid, liquid or gas target, which itself can be part of the detection system. COMPASS, which looks at the structure of hadrons – particles made of quarks – uses beams from the Super Proton Synchrotron (SPS). NA61/SHINE studies the properties of hadrons in collisions of beam particles with fixed targets. NA62 uses protons from the SPS to study rare decays of kaons. DIRAC is investigating the strong force between quarks at the Proton Synchrotron (PS). The CLOUD experiment is investigating a possible link between cosmic rays and cloud formation. ACE, AEGIS, ALPHA, ASACUSA, and ATRAP all use antiprotons from the Antiproton Decelerator, while the CAST experiment is looking for hypothetical particles coming not from collisions at the accelerators but from the Sun.
This diverse research programme ensures that CERN covers a wide range of topics in physics, from kaons to cosmic rays, and from the Standard Model to supersymmety. Find out more about individual experiments in the list below.
ACE brings together an international team of physicists, biologists and medics to study the biological effects of antiprotons
AEGIS uses a beam of antiprotons from the Antiproton Decelerator to measure the value of Earth's gravitational acceleration
ALICE detects quark-gluon plasma, a state of matter thought to have formed just after the big bang
ALPHA makes, captures and studies atoms of antihydrogen and compares them with hydrogen atoms
The Alpha Magnetic Spectrometer looks for dark matter, antimatter and missing matter from a module on the International Space Station
ASACUSA compares matter and antimatter using atoms of antiprotonic helium and antihydrogen, and studies the properties of matter-antimatter collisions
From a cavern 100 metres below a small Swiss village, the 7000-tonne ATLAS detector is probing for fundamental particles
ATRAP compares hydrogen atoms with their antimatter equivalents - antihydrogen atoms
AWAKE explores the use of plasma to accelerate particles to high energies over short distances
Hypothetical particles called axions could explain differences between matter and antimatter - and we may find them at the centre of the Sun
Could there be a link between galactic cosmic rays and cloud formation? An experiment at CERN is using the cleanest box in the world to find out
The CMS detector uses a huge solenoid magnet to bend the paths of particles from collisions in the LHC
COMPASS investigates how quarks and gluons interact to give the particles we observe
A collaboration of CERN physicists are studying the decay of unstable “pionium atoms” to gain insight into the strong force
ISOLDE studies the properties of atomic nuclei, with further applications in fundamental studies, astrophysics, material and life sciences
The LHCb experiment will shed light on why we live in a universe that appears to be composed almost entirely of matter, but no antimatter
The LHCf experiment uses particles thrown forward by LHC collisions to simulate cosmic rays
The MOEDAL experiment is looking for a hypothetical particle with magnetic charge: the magnetic monopole
The SPS Heavy Ion and Neutrino Experiment (NA61/SHINE) studies the properties of hadrons in collisions of beam particles with fixed targets
Rare kaon decays can give insights into how top quarks decay – and help to check the consistency of the Standard Model
The neutron time-of-flight facility (nTOF) studies neutron-nucleus interactions for neutron energies ranging from a few meV to several GeV
The OSQAR experiment looks for particles that could be a component of dark matter and explain why our universe is made of matter instead of antimatter
The 'Total elastic and diffractive cross-section measurement' experiment studies particles thrust forward by collisions in the LHC
The UA9 experiment is investigating how crystals could help to steer particle beams in high-energy colliders