About the LHC

Aerial view of the Geneva, Switzerland area, with the 27-kilometer path of the LHC tunnel outlined in red. Image © CERN

An international team has installed the Large Hadron Collider at CERN in a 27-kilometer ring buried deep below the countryside on the outskirts of Geneva, Switzerland. The LHC is the world’s most powerful particle accelerator. Its very-high-energy proton collisions are yielding extraordinary discoveries about the nature of the physical universe. Beyond revealing a new world of unknown particles, the LHC experiments could explain why those particles exist and behave as they do. The LHC experiments could reveal the origins of mass, shed light on dark matter, uncover hidden symmetries of the universe, and possibly find extra dimensions of space.

Billions of protons in the LHC’s two counter-rotating particle beams smash together at an energy of 14 trillion electron volts. After injection into the accelerator, the hair-thin proton beams accelerate to a whisker below the speed of light. They circulate inside for hours, guided around the LHC ring by thousands of powerful superconducting magnets. For most of their split-second journey around the ring, the beams travel in two separate vacuum pipes, but at four points they collide in the hearts of the main experiments, known by their acronyms: ALICE, ATLAS, CMS and LHCb.

The experiments' complex detectors will eventually see up to 600 million collisions per second, as the energy of colliding protons transforms fleetingly into a plethora of exotic particles. In the data from these ultrahigh-energy collisions scientists from universities and laboratories around the world search for the tracks of particles whose existence could transform humankind's understanding of the universe we live in.