Number 229 (Story #1), June 7, 1995 by Phillip F. Schewe and Ben Stein A NEW MEASUREMENT OF THE MASS OF THE W BOSON has been carried out by the CDF collaboration at the Fermilab collider. The data sample consists of thousands of events in which the charged W's are produced in high energy proton-antiproton collisions and then each decay into a neutrino plus either an electron or muon. The W's, along with the Z boson, are the carriers of the weak nuclear force. Now that the top quark has been discovered, the next major quarry in particle physics is the Higgs boson, the particle which supposedly endows other particles with mass. Theorists believe that measurements of the top quark mass and the W mass can be used to constrain estimates of the likely Higgs mass. This knowledge, in turn, tells scientists whether they could hope actually to produce the Higgs at an accelerator, assuming that the Higgs exists as a physical particle. The new W mass measurement (80.410 GeV) has only half the uncertainty of the best previous mass measurement. (F. Abe et al., 3 July 95, Physical Review Letters.)