Largest Machines On Earth: Particle Colliders

Cornell University physicist Maury Tigner, director of Cornell's Laboratory for Elementary Particle Physics (LEPP) in Ithaca, N.Y., is playing a major role in two of these machines: the Large Hadron Collider (LHC), being built at the European Centre for Nuclear Research (CERN) in Geneva, for which he serves as chairman of the machine advisory committee, and the International Linear Collider (ILC), being planned by an international team, for which he is chairman of the steering committee.

Tigner describes the two machines today (Feb. 19) at the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington, D.C., in a talk on "The Highest Energy Particle Colliders."

Tigner is well-known internationally as the first physicist to propose the idea for linear particle accelerators -- in 1965. He will open his talk by discussing the reasons for building such colossal and expensive machines to study the ultimate building blocks of all matter, and in particular to search for the Higgs boson, known as the God particle because of its postulated commanding role in explaining how subatomic particles interact with each other.

LHC is nearing completion in the 27-kilometer (17 miles) circumference tunnel originally created for CERN's Large Electron Positron collider. When completed in 2007, LHC will be the largest such device on Earth. It will slam protons (one type of hadron particle) together with an energy "seven times that of the largest such collider running now, the [the Fermi National Accelerator Laboratory] Tevatron, outside Chicago," says Tigner.

He also hopes the LHC will help scientists answer such questions as: Where does mass come from? What is the dark matter that permeates most of the universe? How many dimensions do we need to describe the physical world?

The ILC, a multibillion-dollar colossus that will require unprecedented international scientific cooperation, will be complimentary to CERN's LHC. The ILC actually would be two linear accelerators colliding electrons and positrons in a tunnel 40 kilometers (25 miles) long, 10 times as long as the current longest linear particle accelerator, the Stanford Linear Accelerator (SLAC).

"The advantage of a machine that collides electrons and positrons together is that, unlike protons, they are elementary particles, so you know exactly what the energy is in any reaction that you see," says Tigner. "Certain phenomena can only be seen with electron and position collisions. Thus ILC will make a good discovery machine."

He notes, "The main function of ILC is to quantify and pin down the identities and true nature of particles seen in both machines."

He adds that accelerators also are being used in areas of science beyond particle physics, from molecular biology to nanotechnology. "The work on accelerators in one field has synergy for work in other fields," says Tigner. As just one example, he cites the prototype for ILC that has been built by Deutsches Elektronen-Synchrotron (DESY) in Hamburg, a machine that also is being used as a free-electron laser making ultraviolet light for chemistry and condensed matter physics.