The Meson Mystery

The University of California admitted last week (after too many garbled rumors in the press) that it had created the first man-made meson. U.C. did it with its 4,000-ton cyclotron. The news caused a sizable flurry throughout the world of physics--for mesons are closely connected with the unknown force that holds matter together.

Mesons are mysterious, short-lived particles knocked out of .atomic nuclei. It takes a lot of punch to knock them out. Before the 4,000-ton cyclotron developed sufficient punch, the only mesons in captivity had been trapped in the wild. Dr. Carl Anderson of CalTech found their characteristic tracks in a cloud chamber. Other scientists found two types, heavy and light, in photographic plates exposed on high mountains. All had been formed by cosmic rays, the enormously powerful particles that strike down out of space. No man-pushed particle was strong enough to engender a single meson.

The great cyclotron at Berkeley is just barely strong enough. Dr. Eugene Gardner, 35, and Brazilian-born Dr. C.M.G. Lattes, 23, put a thin carbon target in a beam of alpha particles (helium nuclei) in the cyclotron chamber. Figuring that the alpha particles had enough power (380 million electron volts) to knock mesons out of the carbon atoms, Gardner & Lattes put a stack of special photographic plates at the spot where the mesons should hit. Then they turned on the cyclotron. When they developed the plates, they found the characteristic wavy tracks of negative mesons. Some of them ended in "stars," the atomic X-marking-the-spot where a meson has entered the nucleus of an atom and exploded it to bits.

Drs. Gardner and Lattes have not as yet discovered anything new about their man-made mesons. But their achievement has excited nuclear physicists all over the world. For the first time they have access to mesons, and can study them under controlled laboratory conditions. A technical advance of this sort has often led to important theoretical discoveries.

Atomic Energy Commissioner Robert Bacher says that the discovery has nothing directly to do with the release of atomic energy. "It wouldn't be in the papers if it had." Not now, perhaps. But mesons are intimately concerned with the way that matter turns into energy and vice versa. They are not believed to exist already formed in a normal nucleus, but are created somehow when an energetic particle smashes into the unknown but enormously powerful field of force that holds the nucleus together. Study of mesons may tell what this force is. The next step (in the usual sequence of things) may be control of the force. This may lead in the direction of a vastly better source of atomic energy than the fission of uranium.

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