Secret Uncovered

At a conference in Kiev, Russia. Physicist Luis Alvarez of the University of California last week held up a strange photograph that looked a little like a nonobjective drawing. It was in fact a picture of one of nature's innermost secrets. Made possible by use of California's new 6-ft. liquid hydrogen bubble chamber (TIME, July 13), it showed for the first time the birth, death and after effects of an anti-lambda particle.

Lambda particles are short-lived packets of matter created when high-energy protons hit protons at rest. Since each particle is presumed to have its "anti" counterpart, scientists have long been looking for anti-lambda. Faint traces of the elusive particle showed last year on photographic plates exposed to the 6 billion-volt Berkeley Bevatron, but the plates were too small to tell much of the anti-lambda story.

In the bubble-chamber picture (see cut), an antiproton from the Bevatron enters at bottom and hits a proton (1): out of the collision come one lambda and one anti-lambda particle. Since both are neutral electrically, they leave no tracks in the liquid hydrogen, but after a short, invisible career, each decays into track-leaving particles by which it can be identified. The lambda ( 2) turns into a proton and a negative pi meson, both of which go off the picture leaving strong curved tracks. The anti-lambda (3) turns into an antiproton and a positive pi meson. The positive pi meson goes off the picture, but the antiproton hits a proton (4), creating two negative and two positive pi mesons, which shoot up and down the chamber.

Identifying anti-lambdas and their relatives is no mere collecting program, like filling out a series of postage stamps. The behavior of each new particle can be studied, yielding bits of knowledge not only about ordinary matter but about antimatter as well. It may have anti-gravity threading through its masses. There is even a possibility--something to think about, at least--that in the strange world of antimatter, time may run in reverse.

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