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Physics: The Eightfold Way

3 minute read

The esoteric world of theoretical physics went into spasms of enthusiasm last week when Brookhaven National Laboratory announced the identificationof a new elementary particle. It is not the biggest particle known or the smallest, and it lives only one ten-billionth of a second. But physicists all over the world were stirred up because it has almost precisely the mass that was predicted for it by long-range theory. It was rather as if Columbus, sailing across the Atlantic, had really found Japan just where he thought it would be.

Plethora of Particles. For years physicists have been confused by the largely accidental discovery of more and more particles. They appear in the smashed-up debris of collisions between other particles, and they show up clear and sharp on bubble-chamber pictures and other detection devices. By the time about 100 such bits of matter had been found, physicists began to doubt that they were really elementary. Questions arose. Were some of the particles merely “states” of other particles, differing in only minor ways? Were they all just combinations of a few really elementary particles? No one knew for sure; no general law relating the particles to one another could be proved true.

One of the most promising attempts to devise such a law was made by Physicists Yuval Ne’eman of Israel and Murray Gell-Mann of Caltech, with a contribution from Japanese-born Susumu Okubo of the University of Rochester.

Called affectionately the “eightfold way,” from Buddha’s list of eight virtues that lead to the cessation of pain, the theory is based on eight quantum numbers or fundamental properties that can be used to describe particles. The reasoning that supports the eightfold way is advanced quantum mechanics and beyond the understanding of the mathematically unanointed, but one of the predictions of the “way” was clear enough: a particle must exist that has a negative electric charge and a mass— of 1,676 million electron volts. It should have a life span of one ten-billionth of a second after it is formed, and then decay into a xi particle and a pi-meson.

Omega-Minus Signature. The unknown particle predicted by the eightfold waywas named omega minus, and both CERN Laboratory in Geneva and Brookhaven National Laboratory on Long Island started elaborate campaignsto find it. Brookhaven’s apparatus was built around the 33-bev (billion electron volt) Alternating Gradient Synchrotron, and it used a line of magnets and electrostatic separators 400 ft. long to isolate negative K-mesons. Ten of the K-mesons were allowed to enter Brookhaven’s 80-in. liquid-hydrogen bubble chamber every 2½ seconds, and pictures were taken of the results. Two pictures out of 100,000 showed tracks in the LH2 that proved to be the “signatures” of omega-minus particles. They all curved just right and took off in the right directions. Careful calculations with a computer gave the mass of the new-found particles as 1,686 plus or minus 12 mev. This was almost uncanny agreement with the predictions of the eightfold way.

Omega-minus particles will never be made into rocket fuel or nuclear weapons. Their life (10 -10 sec., as predicted) is too short. But their discovery by a guiding theory has given an enormous boost to physics. Now that the eightfold way has been checked by this striking success, it can be used as a trusty tool in the search for more discoveries.

*Since mass is equivalent to energy, theoretical physicists like to measure the mass of a particle in electron volts. The mass of one electron at rest is .511 million electron volts.

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