Large Hadron Collider

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"LHC" redirects here. For the pop group, see Les Horribles Cernettes

The Large Hadron Collider (short LHC) is a particle accelerator and collider located at CERN. It is currently under construction and scheduled to start operation in 2007. It will become the world's largest particle accelerator. It uses the 27 km circumference tunnel created for the Large Electron Positron (LEP) collider. In contrast to the previous it will collide protons (one type of hadron particle) instead of electrons and positrons. The protons used will have an energy of 7 TeV each (total collision energy of 14 TeV). Five experiments will be built to utilize the LHC. Two of them, ATLAS and CMS are large, "general purpose" particle detectors. The other three (LHCb, ALICE, and TOTEM) are smaller and more specialized.

The LHC can also be used to collide heavy ions such as lead (Pb) (collision energy will be 1150 TeV).

Physicists hope to use the collider to answer the following questions:

What is mass? (We know how to measure it - but what is it?)

What is the origin of mass of particles? (In particular, does the Higgs Boson exist?)

What is the origin of mass of baryons? (By creating the quark-gluon plasma one will test the non-perturbative origin of a large fraction of the mass of the universe)

Why do elementary particles have different masses? (I.e., do particles interact with a Higgs field?)

We know that 95% of the universe's mass is not made of matter as we know it. What is it? (I.e. what is dark matter, dark energy?)

Do supersymmetric (SUSY) particles exist?

Are there extra dimensions, as predicted by various models inspired by string theory, and can we "see" them?

Are there additional violations of the symmetry between matter and antimatter?

The LHC is of immense size and represents a huge, and potentially dangerous, engineering task. On October 15, 2005, a technician was killed in the LHC tunnel when a crane load was accidentally dropped [1],[2].