Large Hadron Collider

The LHC is a circular accelerator located in a tunnel about 100 metres underground at CERN, on the Franco-Swiss border near Geneva. The ring is approximately 27 kilometres in circumference. Radiofrequency structures accelerate particles, while superconducting magnets bend and focus the beams. The magnets operate at temperatures near 1.9 kelvin, requiring cryogenic systems. Two beams travel in opposite directions in separate evacuated beam pipes and are brought into collision at designated interaction points.

The LHC accelerates protons and, in some runs, ions such as lead nuclei. CERN's accelerator chain prepares particle beams before injection into the LHC. Detectors surrounding collision points record particles produced in collisions. ATLAS and CMS are general-purpose experiments; ALICE and LHCb are designed for more specialized studies. The experiments are operated by international collaborations of research institutes.

High-energy collisions allow researchers to test predictions of the Standard Model and investigate questions that the model does not resolve. On 4 July 2012, the ATLAS and CMS collaborations announced the observation of a new particle. Further analysis found that its properties were consistent with the Higgs boson. The discovery provided evidence for the Higgs field, while ongoing measurements of particle production and decay continue to test theoretical predictions.