The key elements of the SLC are an extensive upgrade to the existing two-mile linear accelerator to produce 50 GeV beams of both electrons and positrons, two small storage rings that are used to damp the beams down to suitable dimensions, two long curving arcs of magnets that are used to transport the separate electron and positron beams from the end of the linac to a single collision point, and an elaborate focusing system that reduces the sizes of the colliding beams down to dimensions much smaller than a human hair. In 1992 a new polarized source was developed with very high intensity. The following year it was upgraded to generate highly polarized beams, which allow sensitive studies of the Z0 particle.
The first detector system used with the SLC (called MARK II) had been upgraded after earlier use at both SPEAR and PEP. A much more elaborate and complete detector system called the SLC Large Detector, or SLD, was installed in 1991. The SLD will insure that the SLC experimental program remains productive into the mid-1990s.
The European community has chosen to achieve collisions between 50 GeV electron and positron beams through the use of the more conventional storage-ring technique at the CERN laboratory near Geneva, Switzerland. Their Large Electron Positron collider (LEP) machine is a storage ring some 17 miles in circumference; it has the advantage of four interaction regions (rather than one at the SLC) and the possibility of a higher ultimate energy. The SLC, on the other hand, has a polarized electron beam and a collision spot with an area hundreds of times smaller than that of LEP, opening new physics areas to the SLC.
Early research results from the SLC and LEP have already begun to prove the value of these colliders. The mass and other properties of the Z0 particle, which is a carrier of the weak force of subatomic physics, have been determined to unprecedented precision. Even more important, this early work has determined with high probability that the universe is in fact made up of not more than the three known families of elementary particles (each with two kinds of leptons and two kinds of quarks).
The SLD is collecting data on the production of the Z0 boson using a polarized electron beam. This will lead to the most precise measurement of a crucial parameter in particle physics theory as well as unique measurements on B-mesons. Recent running with SLD has shown a predicted preference for producing the Z0 when the beam is polarized with the spins rotating about the beam axis in a left-handed sense. This distinction at the most fundamental level between left- and right-handedness is one of the most intriguing phenomena in subatomic physics.