LEP is Now Making Pairs of W Bosons

Shortly after noon on 9 July, an important new experimental regime of high‐energy physics was inaugurated with the first observation of a $W+W−$ pair at CERN's Large Electron‐Positron (LEP) collider. The charged W's and their neutral cousin, the $Z0,$ are the three spin‐1 bosons that mediate the weak interactions. Because they are almost 100 times heavier than the proton, these “intermediate vector bosons” present a particular challenge to accelerator builders and experimenters. Though their existence and their masses were predicted by the Glashow‐Salam‐Wemberg unification of the electromagnetic and weak forces in the late 1960s, they could not be observed until the 540‐GeV CERN proton‐antiproton collider was completed in the early 1980s. (See PHYSICS TODAY, November 1983, page 17).