Number 111 (Story #3), January 21, 1993 by Phillip F. Schewe and Ben Stein HOW ELEMENTARY PARTICLES COME TO HAVE THE MASS THEY DO is "the most important outstanding problem in particle physics today," says Berkeley scientist Lawrence Hall. The standard model is not much help: indeed, certain of the known particle masses are used as input parameters for the theory. Hall and his colleagues Savos Dimopoulos of Stanford and Stuart Raby of Ohio State have advanced a new model, reworking parts of the existing theories, which makes six specific testable predictions (Phys. Rev. Lett., 30 Mar. 1992) on such topics as B-meson decay, proton decay, and the top quark (their estimate for the mass: 188 GeV). The top is being pursued at Fermilab and new proton-decay experiments are being readied in Japan---the Super Kamiokande detector---and Italy---the Icarus detector. (Science, 8 Jan. 1993.)