Physics:Gotcha!

It was once called the great white whale of physics. The longer the "top" quark managed to elude capture, the more obsessed its pursuers became with the importance of hunting it down. For in the subatomic world, the top was, scientists believed, the sixth and last of the quarks -- pointlike particles that constitute the basic building blocks of matter. As the years passed, failure to find the top became a source of consternation and potential embarrassment to the theorists who swore it must exist.

But last week the scientific equivalent of "thar she blows" echoed around the world. The news came from several hundred particle hunters working at Fermi National Accelerator Laboratory near Chicago, who presented compelling evidence that not one but 12 top quarks had briefly surfaced inside a mammoth detector in their lab.

The first sightings of this long sought trophy have still to be confirmed, but when they are, they will culminate one of the richest periods of discovery in the history of science. They will also justify the confidence physicists have placed in the so-called Standard Model, a powerful theoretical edifice that has reduced a once bewildering array of subatomic particles to just a few fundamental constituents. These include three pairs of light particles known as leptons, of which the negatively charged electron and chargeless neutrino are the most familiar, and three pairs of heavier particles known by the whimsical name of quarks. "Up" and "down" quarks combine to create protons and neutrons, the components of everyday matter, while "charm" and "strange" quarks conspire to make more exotic particles, the sort produced in deep space by quasars and high-energy cosmic rays. In 1977, when a fifth quark called "bottom" was discovered, physicists quickly deduced that it too must have a partner.

That partner turns out to be well worth years of searching. Its apparent characteristics contain intriguing hints of an unexplored microcosmos, one that may be populated by particles far odder than any discovered to date. For the top quark is extraordinarily heavy. It is, to be exact, 200 times heavier than a proton and almost as hefty as an entire atom of gold. That an elementary particle can weigh so much, says University of Chicago physicist Henry Frisch, amounts to a "tantalizing clue." It suggests that the top is intricately entwined with the mysterious mechanism that is responsible for creating mass.