Enlarging the Zoo

"I've got some very exciting physics to tell you," said M.I.T. Physicist Samuel Ting earlier this month as he entered the office of Burton Richter, a Stanford University physicist. "Listen," Richter interrupted, "I've got some exciting physics to tell you." In fact, the two researchers, working independently and a continent apart, had almost simultaneously made an important discovery: a totally new type of subatomic particle that could upset prevailing ideas about the basic nature of matter.

Physicists have already discovered some 200 elementary particles, usually by smashing apart nuclei of atoms in huge accelerators. Most of the particles live for only a tiny fraction of a second before they decay into more stable atomic components Like electrons. Until now, all of these particles have occupied predictable places in what physicists jocularly call their subnuclear "zoo." The puzzling new discovery is a total misfit.

Tentatively called a "J" particle by Ting's team, which used the 33 billion-electron-volt accelerator at the Brookhaven National Laboratory, and a "Psi" particle by Richter's group at the two-mile-long Stanford Linear Accelerator, it was the heaviest atomic fragment ever found--almost 3% times more massive than the proton. It was also, by nuclear standards, extremely long-lived. It survived a full one-hundred billionths of one-billionth of a second, or 1,000 times longer than other massive particles.

Excited theorists speculated that the particle could be the long-sought Link between two of nature's basic forces, electromagnetism and the so-called nuclear weak force, which shows up in some types of radioactivity. Others suggested that it may be the first member of a whole new family of subatomic particles possessing a new physical property whimsically named "charm." If such particles really exist, they would, in turn, be made up of a new "charmed" form of quarks and antiquarks--elusive fragments that have been hypothesized as the basic building blocks of all matter. By week's end that speculation took on dramatic new significance when Richter's team announced the discovery of still another new particle even more massive than the original Psi (or J) and said the hunt was on for others.

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