Scientists Detect Tau Particle

July 21 -- In what is being hailed as a heroic achievement in physics, scientists have found the first direct evidence of the tau neutrino, an elusive and ghostly subatomic particle that was thought to be the last missing piece in the architecture of matter.

The breakthrough, announced on Thursday, was achieved by scientists at the Fermi National Accelerator Laboratory outside Chicago.

“It’s a tremendous milestone,” said Stanford University physicist and Nobel Prize winner Martin Perl, who first theorized the existence of the tau neutrino in 1978. “Now it has been seen, and it behaves in the way we expected.”

Since 1997, fifty-four scientists from the United States, Japan, Korea and Greece collaborated on tracking down the tau neutrino at the Fermi Laboratory.

Final Building Block

The tau is one of the fundamental building blocks of all matter. It is the 12th and last of the impossibly tiny particles described in the Standard Model of Particle Physics to be confirmed in experiments.

The standard model seeks to encapsulate all elementary particles and forces in a single explanation. Now the bits have been identified, though the many forces that guide their interplay remain a mystery.

“We finally have direct evidence that the tau neutrino is one of the building blocks of nature,” said Byron Lundberg, a physicist and spokesman for the international team. “It is one thing to think there are tau neutrinos out there. But it is a hard experiment to do.”

Perl said there may be other types of neutrinos out there, but they have not been identified or even theorized.

Finding the tau has no immediate practical applications. But physicists were thrilled.

“No one doubted the existence of the tau neutrino, but finding it is a heroic accomplishment,” said astrophysicist John Bahcall of Princeton University and the Institute of Advanced Studies.

Everywhere, But Elusive

Neutrinos are hurtling everywhere and all the time at nearly the speed of light. Every second, trillions pass through all of us and the Earth itself.