Il Large Hadron Collider

As particle physics heads towards the 21st century, its focus is evolving from seeking the basic constituents of matter, to discovering why these constituents are the way they are. The Large Hadron Collider (LHC), being built at CERN, is the machine that will take particle physicists into this exciting new phase of discovery.

Theory strongly indicates that answers to some of the remaining questions will begin to emerge at energies of around 1 TeV (tera electron volt). This is a million million times the energies typical of biological and chemical processes, but only about ten times greater than those currently accessed at particle accelerators. These are the energies the LHC will explore.

The easiest way to reach 1 TeV is by colliding together proton beams, as protons are relatively easy to produce and to accelerate. However, protons are complex objects, containing quarks and gluons (carriers of the strong force) amongst which the energy is shared. So to reach energies in the region of 1 TeV, the LHC will collide proton beams with higher energies, around 7 TeV.

CERN has a tradition of building new machines that capitalise on previous investments by exploiting existing accelerators. LEP incorporates the PS, the laboratory's first proton accelerator built some 40 years ago, as well as the Super Proton Synchrotron (SPS) which was constructed during the 1970s. The LHC will also make full use of these accelerators, which will act as injectors. Moreover it will be built in the LEP tunnel, so no major civil engineering will be required. To start with, LHC will be installed in place of LEP. Later, LEP might be reassembled with the LEP magnets installed on top of the LHC magnets, thus opening new research possibilities by having LHC/LEP combined operations.