Newspaper article The Christian Science Monitor

Physicists Confirm Quark That `Had' to Be There

Newspaper article The Christian Science Monitor

Physicists Confirm Quark That `Had' to Be There

Article excerpt

AN international collaboration of more than 440 scientists has announced the most reliable "sightings" yet of an elusive member of the first family of elementary particles thought to make up matter. They call it the "top" or "truth" quark.

It is the only one of 12 basic particles called for in the current standard theory of matter that had not been produced, weighed, and measured in the laboratory. Now the collaboration has enough evidence, produced at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., to specify its probable mass. It weighs in at about 187 times the mass of a hydrogen atom - about the same as the element rhenium and a little lighter than gold. It's the heaviest particle known. Sense of relief

Physicists are greeting this long-anticipated discovery with more of a sense of relief than of surprise. Theorist John Bahcall at the Institute for Advanced Study in Princeton, N.J., notes that the mass is in the range expected. But if the top quark had not been found as expected, he says, "then everything we know {about the basic nature of matter} wouldn't make sense." Seen in this perspective, Dr. Bahcall calls the work "a magnificent achievement ... {marking} an end of an era and beginning of a new era" for research that goes beyond what the standard theory covers.

Briefly, that theory involves two sets of six basic particles. There are three electron-like particles - the ordinary electron and the muon and tau particles. These are associated with three neutrinos - electrically neutral particles having little or no mass. There are also six quarks called up, down, charm, strange, bottom (or beauty) and top (or truth). The new knowledge about the top quark, if confirmed by further experiments, completes the evidence for this scheme.

Most matter, as we know it, is made up of the ordinary electron and the up and down quarks. …

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