Super-Kamiokande Determines the Existence of Neutrino Mass
On October 6, 2015, all Japanese people were delighted to hear the news that Dr. Takaaki Kajita won the Nobel Prize in Physics. He is the director of the Institute for Cosmic Ray Research (ICRR) at the University of Tokyo and member of the Super-Kamiokande experiment group which discovered that the neutrino (*1), one of the most elementary particles in the universe, has mass.
This is a groundbreaking discovery that disproves the widely accepted Standard Model of particle physics which states that neutrinos do not have mass. He is the second Japanese to receive the Nobel Prize in Physics for research on neutrinos, following Dr. Masatoshi Koshiba, who observed neutrinos from a supernova for the first time in the world. Dr. Kajita is a pupil of Dr. Koshiba.
The Super-Kamiokande detector (completed in 1996) built 1,000 meters underground in Hida, Gifu Prefecture, is the observation facility that determined that neutrinos have mass. Super-Kamiokande, the successor to the Kamiokande detector (completed in 1983), has a significantly improved capability to detect neutrinos with its larger size and enhanced sensor functionality. Mounted on the inner wall of Super-Kamiokande are 11,000 photo-multiplier tubes with a diameter of about 50 cm. These photo-multiplier tubes are operated 24 hours a day to capture extremely dim flashes of light generated when a neutrino collides with a water molecule, which occurs infrequently.
*1: A type of fundamental particle. The name combines "neutral," indicating that it is neutral—carrying no electric charge—and "ino," Italian for "small." Although it is one of the most elemental of fundamental particles, its nature is very poorly understood.
Accumulating and Analyzing Massive Data on Neutrinos
Super-Kamiokande observes solar neutrinos, atmospheric neutrinos, and even supernova neutrinos, which can be detected only once in several decades and for only a dozen seconds. In order to ensure these neutrinos are observed, the systems are required to operate stably for 24 hours a day, 7 days a week and process analytical data at a high speed. Fujitsu has been supporting such neutrino research with its experiment-analysis systems (*2) since the beginning of the experiment in 1996.
The experiment-analysis systems currently in operation enable the storing of massive processed observation and analysis data of up to 500 GB per day reliably. They also provide access to a huge volume of historical data at a high speed. In addition to making analysis more efficient leveraging its high reliability and improved data transfer and processing performance, Fujitsu’s experiment-analysis systems also reduce power consumption.
*2: The systems are mainly comprised of the PC cluster system using 142 units of Fujitsu’s blade server "PRIMERGY BX922 S2," the "ETERNUS DX80 S2" storage system and a high-speed distribution file system using scalable file system software FEFS.
Further Studies on the Nature of Neutrinos
A deeper understanding of the nature of neutrinos is expected to provide important clues to understand the building blocks of the universe and the origin of matter. Moreover, it may help researchers search for the ever-elusive proton decay or realize experiments to verify the Grand Unified Theories (*3), which no one has ever been able to do.
Currently, a new project is already underway to develop the Hyper-Kamiokande detector which consists of a megaton scale water tank and ultra-high sensitivity photo-sensors. The experiment is slated to begin around 2025.
The current computer systems for the Super-Kamiokande experiment are actually the fifth generation. Fujitsu will continue to contribute to efforts made to solve the mysteries of the universe by supporting neutrino research leveraging the power of ICT.
*3: The Grand Unified Theories (GUTs) attempt to unify the interaction of three forces out of the four fundamental forces of nature, namely electromagnetism, the weak nuclear force and the strong nuclear force. These theories have yet to establish a definite model and further experimental verification is expected.