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The Hunt for Neutrinos
How do you track a particle that leaves no footprints?
by Liza Gross

amanda at the south pole
  Photo: John Jacobsen
  Preparing to lower one of AMANDA's light sensors into the ice.

"The hope is that the particle that is almost nothing will tell us almost everything about the universe."
Francis Halzen, principal investigator of the AMANDA detector

Researchers on the trail of the neutrino—the subatomic "ghost" particle notorious for leaving no trace—have cast ever-wider nets to apprehend it. But none of those efforts rival the scale or ingenuity of the ice-bound detective of the Antarctic, AMANDA.

With a mission as ambitious as its construction, AMANDA (Antarctic Muon and Neutrino Detector Array) is a collaborative enterprise involving fifteen universities and science institutes from the United States and Europe. Designed to find evidence of black holes and other deep-space phenomena, this improbable observatory carved into the deep ice of the South Pole promises to advance our understanding of the evolution of the universe.

Neutrino Fundamentals

Neutrinos, like quarks and electrons, are elementary particles, fundamental building blocks of matter. But, unlike their subatomic cousins, neutrinos have no electric charge, nearly no mass, and little affinity for matter. You can't see neutrinos, but you can tell they've been around by the wreckage they leave behind. Like any particle with no charge, neutrinos can be detected only when their interactions produce charged particles. Although a neutrino interaction is rare, when it does happen, it can produce a negatively charged particle called a "muon." Because that muon moves along the same path as the incoming neutrino did, researchers can tell which direction the neutrino came from by examining the muon's trail.

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