First results from upgraded CERN collider.

The hunt for elementary particles of matter entered a new phase this month with the start of operations at the upgraded Large Electron-Positron (LEP) collider at the European Laboratory for Particle Physics (CERN) in Geneva. The LEP collider, which accelerates electrons and positrons in a circular tunnel 26.7 kilometers in circumference, was designed specifically for studying the weak interaction. This fundamental force is responsible for some forms of natural radioactivity and for the production of neutrinos in nuclear fusion reactions. The force is carried by three particles, designated W+, W-, and Z#161#. By studying these particles in detail, researchers hope to detect traces of exotic particles predicted by various theories but not yet found (SN: 4/13/96, p. 231).

For more than 6 years, the LEP collider operated at an energy of about 91 gigaelectronvolts (GeV) to produce electron-positron collisions of just the right energy to create large numbers of Z#161# particles. The resulting data allowed physicists to determine precisely the mass and other characteristics of this particle (SN: 9/29/90, p. 204).

With the addition of new devices for accelerating electrons and positrons, the collider can now reach an energy of 161 GeV, sufficient for producing W+ W-pairs. Though detected occasionally at other accelerators, these W particles can be produced at CERN in much larger quantities with fewer by products.

Each of the four detectors along the LEP ring has already picked up signals characteristic of the creation of W particles.