The Hunting of the Quark

As they probe deeper into the heart of the atom, discovering ever smaller and more mysterious particles and particles within particles, scientists have succeeded in bringing the once stable world of nuclear physics to a state of near chaos. Groping among their new-found lambdas, pions, kaons, sigmas and other bits of matter with strange names and even stranger characteristics, physicists hope some day to restore order by finding a truly elemental particle -- one out of which all the others are made.

The need for this key building block of the universe became so great that in 1962 Physicists Murray Gell-Mann and George Zweig, working independently, devised and described hypothetical particles that would meet all of the necessary requirements. Gell-Mann insisted that his particle, which he called the quark,*was simply a theoretical tool useful in describing the nature of subatomic particles; it did not necessarily have to exist. But ever since, physicists have been searching in vain for a real quark. Now two British scientists, writing in Nature, have suggested that the search for the quark be conducted in the lower ionosphere, 30 miles above the earth.

Mass into Energy. Gell-Mann's quark is an unusual creature indeed. Unlike other known particles, which are electrically neutral or have positive or negative charges that are whole multiples of the basic charge of the electron, quarks would have a charge of either one-third or two-thirds of the unit electron charge. Arranged in different combinations, quarks would form practically any one of the confusing variety of subatomic particles.

Stranger still, as other scientists have deduced, the quarks would be from ten to 20 times as massive as the proton, one of the heaviest of the subatomic particles. But the proton, according to

Gell-Mann's theory, would consist of three quarks. Then why does it contain only a fraction of the mass of the quarks? The answer, physicists believe, is that most of the mass of the three quarks in a proton is relativistically converted into the tremendous energy that binds them together.

This strong attraction of one quark for another has actually hindered the great quark hunt. To split a proton into its constituent quarks, for example, would require an atom smasher at least 30 times more powerful than any yet built by man. But scientists believe that the celestial processes generating cosmic rays are energetic enough to produce free quarks.

Atoms in Oysters. One group of European scientists used a unique, electronically assisted telescope to search for quarks among cosmic-ray particles that strike the earth. The Russians report that a quark-hunting cosmic-ray experiment was carried aboard their Proton 3 satellite. Neither venture was successful. Other scientists have suggested the use of radio telescopes for discovering evidence of quarks produced in highly energetic radio galaxies and starlike quasars.

Argonne National Laboratory physicists have also examined iron meteor ites, air and sea water in a vain attempt to find quarks that had combined with stable atoms. Instead of being electrically neutral, they reasoned, such atoms would have fractional charges imparted by the quarks--enabling scientists to separate them out in an electric field and analyze them. Because quarks would more likely combine with heavier atoms, one scientist has suggested looking for quark-bearing atoms in oysters, which tend to concentrate the heavier elements in the seas.

30 Miles Up. Arguing that others may have been quark hunting in the wrong places, British Physicists J. B. Hasted and M.R.C. McDowell have suggested a new area of search. As quarks rain down on the earth, the British scientists suggest in their Nature article, those with a negative charge combine with oxygen in the ocean to form fractionally charged quark-oxygen atoms. When the quark-oxygen atoms are carried into the air during the normal evaporation and precipitation cycle, they are repelled by the atmospheric electrical field, which extends some 30 miles above the earth's surface, and are driven into the lower ionosphere. The charged atoms should hover above this level, the scientists say, prevented from settling back to earth by the repelling electric field.

Hasted and McDowell propose to capture the quark-oxygen atom by launching a Venus's-flytrap rocket that would open its jaws at an altitude of 30 miles, adsorb the oxygen atoms on an activated charcoal surface and bring them back to earth. Any oxygen atoms combined with quarks could then be identified by examining the sample with a mass spectrometer, which would separate them out because of their odd mass and fractional charge.

If real evidence of quarks is found, says Hasted, "elementary-particle physics will have taken the next great step forward. It's so important to find quarks that it's worth looking anywhere. But we think that it's much easier to look in the lower ionosphere than anywhere else."

* A name that Gell-Mann borrowed from a line in James Joyce's Finnegans Wake: "--Three quarks for Muster Mark!"

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