Michael D. Wheeler
For years, scientists have sought the elusive, weightless particles known as neutrinos.
Neutrinos, which behave somewhat like photons (they can travel without changing direction through matter), are weakly interacting particles and so can travel much longer without interacting with interstellar matter. They are thought by some theorists to hold clues to the origins of the universe. Now two physicists from Columbia University have proposed building a telescope with a magnetic spectrometer that may threaten the logic behind traditional neutrino-detection schemes.
Physicists typically hunt for the mysterious particles by placing detectors underwater, in caves and below ice. Wonyong Lee and Yunsil Ho proposed locating their telescope atop a mountain. It would identify neutrinos so accurately that they would not need the help of ice, water or Earth as a filter.
High-energy neutrino telescopes such as Japan's Super-Kamiokande have not yet proved their effectiveness in detecting the cosmic source of neutrinos. To study neutrinos with a particular cosmic origin, it is necessary to measure the energy and direction of the muon.
Challenging the norm
Lee and Ho are betting on a magnetic spectrometer to accomplish this. They have proposed building an observatory called High-Energy Astrophysics Neutrino Laboratory, which will incorporate a magnetic spectrometer with detectors that measure the direction and momentum of neutrinos. The telescope will not detect a neutrino, but a reaction the neutrino creates. When one of the particles sideswipes an atom, a muon results. Muons emit a brief flash known as Cerenkov radiation. Measuring these flashes provides clues about the direction in which the neutrino is traveling.
Each module in the observatory's detector will have three components: magnets, detectors and tracking chambers. Each detector will have 2-in. photomultiplier tubes on the top and bottom panels.
By observing how a muon's trajectory curves through the magnetic field, researchers hope to determine whether it was a neutrino or its antiparticle and what its energy level was.
Ho and Lee received a $1 million grant from the Korea Science and Engineering Foundation to build a prototype. If it works, they hope to build a full-scale telescope near Kangnung, South Korea.
