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Aging and decay of beauty.

In the gallant whimsy of physicists, when beauty decays, charm may sometimes remain. Don't reach for the Oil of Olay, however; in this context "beauty" and "charm" are "flavors" of quarks. Flavor is the property that makes one kind of quark differ from another. There are six flavors of quarks, and out of various combinations of them, nearly all the many subatomic particles are supposed to be built. Theory says that a beauty quark should decay into a charm quark. According to the July/August CERN COURIER, a recent experiment at the CERN laboratory in Geneva marks the first time such a decay has been directly observed.

In the event, an energetic pi meson entered a silicon detector, striking an atomic nucleus and producing a negatively charged beauty particle (B.sup.-) and a neutral one (B.sup.0). The B.sup.- traveled 437 micrometers and then decayed into a neutral charm particle and a negative mu meson. The B.sup.0 traveled 4,430 micrometers and decayed into a negative charm particle plus an unspecified positive particle. The event is clean and comprehensive, in that all points where the Bs and the charms were produced fall within the detector. Physicists don't always have that kind of luck.

From the lengths of the trajectories of the B particles, the lifetime of negative beauty comes to 0.8 X 10.sup.-13 second, and that of neutral beauty to 5 X 10.sup.-13 second--fleeting, but sic transit gloria mundi [so passes away the glory of the world]. For physicists the important point is that these numbers are slightly less than those calculated for beauty lifetimes from earlier indirect evidence of beauty decays. That is a good thing, as the longer lifetimes had led some physicists to fear that their "standard model" of particle physics, which explains most things very neatly, might need some amendment.
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Title Annotation:quark classification
Publication:Science News
Date:Aug 3, 1985
Words:313
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