February 17, 2006
Scientists Find 1st Neutrinos in Project
TOKYO -- Hoping to unlock the mysteries of black holes and the Big Bang, a team of scientists from Japan and seven other countries has apparently detected its first neutrinos in a multiyear project underway in Antarctica.
The project, dubbed "IceCube," was launched in 2002, but only detected its first neutrinos on Jan. 29, recording the faint flashes of light given off by the particles when they interact with electrons in water molecules, team member Shigeru Yoshida, a cosmic-ray physics professor at Chiba University, said Thursday.
Neutrinos are subatomic particles with almost no mass and no electrical charge that are associated with radioactive decay. They so rarely interact with matter that they can typically pass entirely through the Earth unobstructed.
Scientists want to study the elusive particles because they may hold the key to understanding the explosion of super-massive stars, known as supernovae.
They also may hold secrets to other distant celestial objects, as they are thought to remain relatively intact during their travel through space.
But scientists say detecting neutrinos is tricky. It requires specialized equipment deep underground - shielded by heavy layers of rock from constant infiltration by cosmic rays, which may interfere with detection.
The IceCube project uses holes dug 2,500 meters (8,250 feet) into ice near the South Pole.
By using the vast Antarctic ice cap as a shield against cosmic rays, the team avoids the often prohibitive costs of building a specialized water tank, which is part of the conventional design for such experiments, Yoshida said.
"If neutrinos were obtained this way, it would signal a new breakthrough in the study of the formation of the cosmos," said Shigeru Machida, an honorary professor of elementary particle theory at Kyoto University, who is not involved in the project.
The Antarctic project is important because it should allow scientists to study where in space the neutrinos are coming from and how strongly they bombard Earth, Machida said.
The team has placed 540 detectors in the ice so far - about 10 percent of the planned total of 4,800 to be installed over the next five years, Yoshida said.
Joining the 30 billion yen (US$254.2 million; euro213.6 million) project are scientists from the United States, Britain, Germany, Sweden, Belgium, the Netherlands, New Zealand and Japan.
When complete, the IceCube project, located near the Amundsen-Scott South Pole Station, will be the world's largest neutrino detector, Yoshida said.
The plan calls for building an observatory 1 cubic kilometer (35,000 cubic feet) in size by 2010, about 20,000 times the capacity of the Super Kamiokande neutrino detector in central Japan.
The increased size will make the Antarctic detector much more sensitive, Yoshida said.
Japanese scientist Masatoshi Koshiba won the 2002 Nobel Prize in physics for his work at the Super Kamiokande detector, which discovered neutrinos coming from distant supernova explosions.