August 4, 2000

Physicists Announce Discovery of a New Fundamental Particle

By RICHARD MONASTERSKY

An international team of 54 physicists announced last month that it had finally found clear evidence of the tau neutrino -- a wraithlike building block of matter that had escaped detection for decades. The discovery fills the last spot in the roster of known fundamental particles that make up the universe.

Neutrinos are so ethereal that trillions of them forged inside the sun sail through our bodies each minute, almost never hitting any atoms. They carry no