The Most Wanted Particle

After a 15-year search, the elusive but extremely heavy top quark may have been found

Imagine an infinitesimal particle that is as heavy as a large atom and less tangible than a shadow. For 15 years, hundreds of physicists have been chasing such an improbable phantom. Their quarry is the top quark, the sole missing member of a family of subatomic particles that form the basic building blocks of matter. Of six types of quarks that are believed to exist, five have already been discovered. "The top," says Harvard University theorist Sheldon Glashow, "is not just another quark. It's the last blessed one, and the sooner we find it, the better everyone will feel."

Physicists will...

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