The Large Hadron Collider; July 2000; Scientific American Magazine; by Smith, side bar by Collins; 6 Page(s)

When two protons traveling at 99. 999999 percent of the speed of light collide head-on, the ensuing subatomic explosion provides nature with 14 trillion electron volts (TeV) of energy to play with. This energy, equal to 14,000 times that stored in the mass of a proton at rest, is shared among the smaller particles that make up each proton: quarks and the gluons that bind them together. In most collisions the energy is squandered when the individual quarks and gluons strike only glancing blows, setting off a tangential spray of familiar particles that physicists have long since catalogued and analyzed. On occasion, however, two of the quarks will themselves collide head-on with an energy as high as 2 TeV or more. Physicists are sure that nature has new tricks up her sleeve that must be revealed in those collisions-perhaps an exotic particle known as the Higgs boson, perhaps evidence of a miraculous effect called supersymmetry, or perhaps something unexpected that will turn theoretical particle physics on its head.

The last time that such violent collisions of quarks occurred in large numbers was billions of years ago, during the first picosecond (10-12 second) of the big bang. They will start occurring again in about 2005, in a circular tunnel that runs under the Franco-Swiss countryside near Geneva. That's the year that thousands of scientists and engineers from dozens of countries expect to finish building the giant detectors for the Large Hadron Collider (LHC) and start experiments. This vast and technologically challenging project, coordinated by CERN (the European laboratory for particle physics), which will take the major responsibility for constructing the accelerator itself, is already well under way.