Atomic buffet

摘要

Eavesdrop on a chat between particle physicists today and you could be forgiven for thinking you were in a grocery store. "It looks like a peanut at this resolution," says theorist Gerald Miller of the University of Washington in Seattle, "or a sausage." But zoom in closer, says Xiangdong Ji of the University of Maryland in College Park, and perhaps it looks more like a doughnut, or a spinning cigar. Such discussions are the result of experiments in the US and Germany that challenge current thinking on the shape of the proton. Far from being tidy spherical balls, the experiments suggest protons are squashed out along at least one of their axes. This idea, of an oblate or peanut-shaped proton, has theorists rethinking their approach to the "strong force" that holds nuclei together. "It is as surprising as thinking the Earth was round and finding it is flat," says John Ralston of the University of Kansas in Lawrence.