The best-known hadrons are the baryons such as protons and neutrons hadrons also include mesons such as the pion and kaon, which were discovered during cosmic ray experiments in the late 1940s and early 1950s. The term hadron refers to subatomic composite particles composed of quarks held together by the strong force (analogous to the way that atoms and molecules are held together by the electromagnetic force). The LHC's goal is to allow physicists to test the predictions of different theories of particle physics, including measuring the properties of the Higgs boson, searching for the large family of new particles predicted by supersymmetric theories, and other unresolved questions in particle physics. The LHC primarily collides proton beams, but it can also accelerate beams of heavy ions: lead–lead collisions and proton–lead collisions are typically performed for one month a year. Seven detectors, each designed to detect different phenomena, are positioned around the crossing points. The collider has four crossing points where the accelerated particles collide. At the end of 2018, it was shut down for three years for further upgrades. Between 20, the LHC was shut down and upgraded after those upgrades it reached 6.5 TeV per beam (13 TeV total collision energy). The discovery of the Higgs boson at the LHC was announced in 2012. The first collisions were achieved in 2010 at an energy of 3.5 tera electronvolts (TeV) per beam, about four times the previous world record. It lies in a tunnel 27 kilometres (17 mi) in circumference and as deep as 175 metres (574 ft) beneath the France–Switzerland border near Geneva. It was built by the European Organization for Nuclear Research (CERN) between 19 in collaboration with over 10,000 scientists and hundreds of universities and laboratories, as well as more than 100 countries. The Large Hadron Collider ( LHC) is the world's largest and highest-energy particle collider. Linear accelerators for protons (Linac 4) and lead (Linac 3) Total Cross Section, Elastic Scattering and Diffraction Dissociation

Plan of the LHC experiments and the preaccelerators.

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