Number 7 (Story #1), November 1, 1990 by Phillip F. Schewe and Ben Stein 650,000 Z PARTICLES have been observed in the LEP electron-positron collider in Geneva, Switzerland during a five-month period ending in August. As recently as 1989, when LEP began operations, the number of Z's observed numbered only in the hundreds. The Z is one of the carriers of the weak nuclear force and can be detected only in the aftermath of high-energy collisions between particles; precise measurements (requiring plentiful events) of Z properties contribute to our knowledge of the standard model of particles physics. LEP plans to produce three times as many Z's in 1991. (CERN Courier, October 1990.)