ATOMIC NUCLEUS

Press, Volume C, Issue 29609, 4 September 1961, Page 9

ATOMIC NUCLEUS

New Particle Discovered

(N.Z.P.A.-Reuter —Copyright) WASHINGTON, Sept. 1. The discovery of a new elementary particle of matter which gives important insight into the structure and behaviour of the atomic nucleus has been announced by the United States Atomic Energy Commission. The particle, called the omega meson, was discovered by scientists in the University of California’s Lawrence Radiation Laboratory, at Berkeley, whose research programme is supported by the A.E.C.

The omega, whose existence was predicted several years ago on a theoretical basis, has a lifetime of one one-hundred billionth of a second (one over one followed by 14 zeros). It plays an important part in the structure of protons and neutrons, the basic “building blocks” of atomic nuclei. Like the neutron, it has no electrical charge.

The identification of the particle was achieved through precise measurement and analysis of photographs of the tracks of particles created when antiprotons and protons come together and annihilate.

The omega breaks up into three pimesons (or pions, the lightest weight mesons) immediately after it emerges from the annihilation zone. But as the omega has such a short life, and is electrically neutral, it does not make tracks of its own in the photographs. The scientists therefore had to select photographs in which the event seemed possible, to work back from the observable particles toward the annihilation, and to prove that three observable pions came from the breakup of unobservable omega. About 30,000 photographs were analysed. In 90 of them, analysis showed that the presence of omega was essential to explain the observable phenomena. Dr. Edwin McMillan, a Nobel Prize winner and director of the Lawrence Radiation Laboratory, said: “The discovery of the omega makes possible a major advance in our understanding of the fundamental particles."