Number 6 (Story #1), October 25, 1990 by Phillip F. Schewe and Ben Stein A NEW MEASUREMENT OF THE W BOSON MASS by the CDF (Collider Detector at Fermilab) group at the Tevatron accelerator gives a value of 79.91±0.39 GeV/c². The W and its neutral cousin the Z boson are the carriers of the weak nuclear force and a precise measurement of their masses contributes to a better understanding of the so-called "standard model" of particle physics. The new CDF result, for example, helps to put an upper limit of 220 GeV/c² on the mass of the as-yet-undiscovered top quark. Earlier in the year, Fermilab scientists were able to establish also a lower limit of 89 GeV/c² for the top. (Upcoming article in Physical Review Letters. Contact: Pekka Sinervo, University of Toronto, 416-978-5270.)