This week, Colorado State University physicists celebrated a long-awaited event – the detection of a neutrino in a huge detector deep inside a mountain in Japan. The observation of this type of sub-atomic particle is not unique. Though difficult to do, scientists have detected thousands of these particles in this same detector before, but this one is special. It was man-made, created in a new particle accelerator in Tokai village on the east coast of Japan. The neutrino travelled nearly 200 miles through the Earth’s crust on its way to the deep underground Super-Kamiokande detector, a 12 million gallon tank of water lined with 11,000 ultra-sensitive light sensors. The cross-country experiment is called “T2K,” referring to the beam source in Tokai to the Kamioka Mine that houses the large detector 3,300 feet underground.
Neutrinos were once referred to as “ghost particles” because of their ability to pass through an entire planet unhindered. They are produced naturally in stars, including our sun, and when adding together the mass of the uncountable number of them travelling around the universe it would be more than all the galaxies combined.
“Neutrinos are intricately involved with how the sun burns and provides heat, how nuclear reactors work, and in natural radioactivity,” said Robert Wilson, professor of Physics at Colorado State. “The importance of this new facility is taking the next step to deepen our understanding of the physical nature of the universe we live in.”
The CSU research group is part of a collaboration of U.S. universities that built a 10-ton device that probes the intense neutrino beam just before it dives underground.
“The goal of this experiment is to study how neutrinos transform from one type into another as they travel,” said CSU team leader Professor Walter Toki. “The ability of the T2K experiment to generate a controlled intense beam is essential to understanding this process. In particular, we hope to see the first evidence of a transformation of a muon-type neutrino produced in an accelerator into an electron-type neutrino like those produced in the sun and nuclear reactors.”
Nearby to Super-Kamiokande is the KamLAND neutrino detector, which is the long-time project of CSU Professor Bruce Berger, also a T2K experimenter.
“KamLAND provided conclusive evidence that neutrinos from nuclear reactors do transform,” said Berger. “We hope T2K will fill in the next piece of the puzzle, finding a much rarer neutrino transformation.”
Even though T2K has just started a five-year program of collecting data, Wilson already has his eyes on the future. In 2006, he and Stony Brook University professor Chang Kee Jung led an unsuccessful Colorado bid for a new Deep Underground Science and Engineering Laboratory (DUSEL) that would have provided the United States with a much larger facility than T2K. Now, Wilson is part of the team developing a design that would send a neutrino beam from Fermi National Accelerator Laboratory near Chicago to a detector 20 times larger than Super-Kamiokande 1,500 miles away and 5,000 feet deep in the Homestake gold mine in Lead, S.D. If approved for funding it will take eight years to complete and another five to 10 years to collect the data they seek, but Wilson explains that it will be worth the wait to unlock a few more of nature’s deepest secrets.