How do particles put on weight?

Some particles are heavier than others, say a trio of theorists, because they are first in line to fill their plate at the source of mass Why are some things heavier than others? In the case of people, the answer clearly has a lot to do with what gets plunked down on the dinner table. For fundamental particles, however, the answer has never been obvious. In fact, it's so mysterious that the brightest physicists have been scratching their heads for decades trying to figure it out. "The problem of mass," says Lawrence Hall of the University of California, Berkeley, "is the most important outstanding problem of particle physics today." But some recent work may give at least partial relief to these frustrated physicists. And the surprising answer may be that particles, like people, have different appetites! Or, to put it another way, they get treated rather differently at the table: Some can Lept fill their trenchers at the source of eleit all mass, while others must be satisfied with left-overs. That at least is the conclusion of muoi a trio of physicists whose work has neutr been causing a stir in the small but muor highly competitive world of theoretical physics. The trio, Savos Dim-opoulos ofStanford University, Hall ofBerkeley, and Stuart Raby ofOhio State University, has conceived what Hall argues is "the most predictive scheme known" for figuring out the masses of elementary particles. If their model holds up, it could fill a substantial void left by the conceptual framework that currently holds all oftheoretical physics together-the Standard Model, for which Sheldon Glashow of Harvard University shared the 1979 Nobel Prize. Glashow himself isn't betting against them: "They're very, very good physicists," he says. And, to top it off, their scheme is testable-no small qualification in the eso-teric world of theoretical physics. Even before the new insights, physicists suspected that elementary particles gained weight by interacting with other, hypothetical particles called Higgs bosons, after the Scotsman who first postulated their existence , Peter Higgs of the University of Edinburgh. "In a manner of speaking," wrote Martinus Veltman ofthe University ofMichi-gan in Scientific American, "particles 'eat' the Higgs boson to gain weight." This picture, now part of the Standard Model, even enabled physicists to explain the weight of two rare particles, the W and Z particles, which are involved in radioactive decay. But that's where the explanatory success ended. Physicists simply …