Stanford’s Gamble Pays Off as Collider Produces Elusive ‘Z’

Several years of efforts to turn a scientific antique into a revolutionary tool to explore the world of high-energy physics have paid off with the production of a subatomic particle called the “Z” by the Stanford Linear Collider, officials announced Wednesday.

The collider, which incorporates a 20-year-old particle accelerator that stretches for two miles into the hills behind the campus of Stanford University, has been plagued with troubles because so many of its components are old and outdated. For awhile, it appeared that it might not succeed in producing elusive “Z” particles, one of the most exotic particles in nature.

Last year, Nobel laureate Burton Richter, director of the Stanford Linear Accelerator Center, personally took charge of a special task force to oversee the collider when it appeared in danger of failing to live up to expectations. Although the collider itself is a revolutionary new design, some of its components were so old that it could not operate long enough to produce any “Zs”.

Thus Richter took great joy in announcing Wednesday that it had finally produced one “Z.” It will need to do that many thousands of times, however, if it is to give scientists an adequate supply to study the properties of Z particles, believed to be one of three “carriers” of the weak nuclear force that is responsible for such things as radioactive decay.

“Many months of hard work lie ahead before we can bring this first-of-its-kind accelerator to its design performance,” Richter said.

Violent Collisions

“Z” particles survive only momentarily in the debris of violent collisions of electrons and positrons, but that brief life is recorded on sensitive detectors so that scientists can study the particles.

Normally, they are produced in conventional colliders that are laid out in the shape of a race track. But the cost of building that type of facility has grown enormously, so Richter came up with the idea of adding an attachment to Stanford’s old accelerator. The attachment is a circle at the end of the linear accelerator. As the beams of positrons and electrons enter the circle, they are split so that they go around in opposite directions and eventually collide.

The concept offered a unique way to achieve high-energy physics at a bargain basement price. But to work, the entire facility had to function flawlessly and on a scale of precision that is virtually unprecedented. Until Wednesday, reaching that goal appeared questionable, at best.

The “Z” produced at Stanford joins a very select community. Since it was discovered in 1983 by an international team of scientists at the European Laboratory for Particle Physics near Geneva, only a couple hundred have been captured there. A few hundred more have recently been produced at the Fermi National Accelerator Laboratory near Chicago.

Richter’s dream had been to have the Stanford collider operational at least a couple of years ago, which would have allowed it to upstage the world’s largest collider, now nearing completion at the European Laboratory for Particle Physics. The European facility cost about 10 times Stanford’s price tag of $115 million.

Despite Tuesday’s success, the chance of beating the European laboratory now appears lost because of the long delays in getting the Stanford facility working, according to sources.

Richter’s friendly rival, Carlo Rubbia, director of the European laboratory who won a Nobel Prize for discovering the “Z” particle, lost no time in congratulating Richter.

“Congratulations and welcome to the club,” Rubbia wired his colleague.