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| Takaaki Kajita and Arthur McDonald Share Nobel in Physics for Work on Neutrinos | |
| (35 minutes later) | |
| Takaaki Kajita of the University of Tokyo and Arthur B. McDonald of Queen’s University in Canada were awarded the Nobel Prize in Physics on Tuesday for discovering that the ubiquitous but elusive subatomic particles known as neutrinos have mass. | Takaaki Kajita of the University of Tokyo and Arthur B. McDonald of Queen’s University in Canada were awarded the Nobel Prize in Physics on Tuesday for discovering that the ubiquitous but elusive subatomic particles known as neutrinos have mass. |
| Neutrinos are the second most abundant subatomic particles in the universe, after photons, which carry light. Their existence was predicted in 1930, but for decades they remained some of the most enigmatic elements of astrophysics. | Neutrinos are the second most abundant subatomic particles in the universe, after photons, which carry light. Their existence was predicted in 1930, but for decades they remained some of the most enigmatic elements of astrophysics. |
| The ghostly neutrino — it means “small neutral one” in Italian — carries no electric charge and is so light that it had been assumed for many years to have no mass at all. The scientists showed that neutrinos, which are found in three “flavors,” could oscillate from one flavor to another — changing identities like a spy on the run, as they traveled through the atmosphere or through space from the sun — demonstrating that they have mass. | |
| Dr. Kajita was part of a team of researchers who in 1998 discovered that neutrinos from the atmosphere switched between two identities on their way to the Super-Kamiokande detector, nearly two-thirds of a mile below the earth’s surface. | Dr. Kajita was part of a team of researchers who in 1998 discovered that neutrinos from the atmosphere switched between two identities on their way to the Super-Kamiokande detector, nearly two-thirds of a mile below the earth’s surface. |
| In 1999, Dr. McDonald announced that neutrinos from the sun were not disappearing, but merely changing disguises, on their way to the earth. He and his colleagues had captured the neutrinos using a uniquely sensitive new detector 6,800 feet below ground, at the Sudbury Neutrino Observatory, which is part of Queen’s University in Kingston, Ontario. | |
| “The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe,” the Royal Swedish Academy of Sciences, which awards the prize, said in a statement. | “The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe,” the Royal Swedish Academy of Sciences, which awards the prize, said in a statement. |
| The universe is swamped in neutrinos that are left over from the Big Bang, and many more are created in nuclear reactions on earth and in the thermonuclear reactions that power the sun. | The universe is swamped in neutrinos that are left over from the Big Bang, and many more are created in nuclear reactions on earth and in the thermonuclear reactions that power the sun. |
| Once thought to travel at the speed of light, they drift through the earth and our own bodies like moonlight through a window. Knowing that they can change identities — and that they have mass — has helped cosmologists understand how the universe has evolved and how the sun works, and it will perhaps help them improve their attempts to create fusion reactors on earth. | Once thought to travel at the speed of light, they drift through the earth and our own bodies like moonlight through a window. Knowing that they can change identities — and that they have mass — has helped cosmologists understand how the universe has evolved and how the sun works, and it will perhaps help them improve their attempts to create fusion reactors on earth. |
| “For particle physics, this was a historic discovery,” the Royal Swedish Academy said in its statement. “Its Standard Model of the innermost workings of matter had been incredibly successful, having resisted all experimental challenges for more than 20 years. However, as it requires neutrinos to be massless, the new observations had clearly showed that the Standard Model cannot be the complete theory of the fundamental constituents of the universe.” | “For particle physics, this was a historic discovery,” the Royal Swedish Academy said in its statement. “Its Standard Model of the innermost workings of matter had been incredibly successful, having resisted all experimental challenges for more than 20 years. However, as it requires neutrinos to be massless, the new observations had clearly showed that the Standard Model cannot be the complete theory of the fundamental constituents of the universe.” |
| Michael S. Turner, a theoretical cosmologist at the University of Chicago, agreed that the Standard Model, a suite of equations that has dominated physics for the last half-century, was not complete. He suggested that neutrinos left over from the Big Bang might make up part of the dark matter that dominates the universe. “Neutrinos contribute about as much to the mass budget of the universe as do stars!” he wrote in an email. “Hooray for neutrinos,” he added. | |
| Dr. Kajita and Dr. McDonald will share the 8 million Swedish kronor, or about $960,000, prize. They joined 199 laureates, including Albert Einstein, Niels Bohr and Marie Curie, who have been honored with the prize since 1901. | Dr. Kajita and Dr. McDonald will share the 8 million Swedish kronor, or about $960,000, prize. They joined 199 laureates, including Albert Einstein, Niels Bohr and Marie Curie, who have been honored with the prize since 1901. |
| Goran K. Hansson, permanent secretary of the Royal Swedish Academy, which appoints the prize committee, announced the prize in Stockholm. | Goran K. Hansson, permanent secretary of the Royal Swedish Academy, which appoints the prize committee, announced the prize in Stockholm. |
| Dr. McDonald, a Canadian citizen born in 1943, was awakened by the Nobel committee and asked to call in to the prize announcement in Stockholm. “It’s a very daunting experience, needless to say,” he told reporters by telephone. “Fortunately, I have many colleagues as well who share this prize with me.” | Dr. McDonald, a Canadian citizen born in 1943, was awakened by the Nobel committee and asked to call in to the prize announcement in Stockholm. “It’s a very daunting experience, needless to say,” he told reporters by telephone. “Fortunately, I have many colleagues as well who share this prize with me.” |
| Informed by phone of the prize, Dr. Kajita, who was born in 1959 in Japan, and directs the Institute for Cosmic Ray Research at the University of Tokyo, said simply, “Kind of unbelievable!” | Informed by phone of the prize, Dr. Kajita, who was born in 1959 in Japan, and directs the Institute for Cosmic Ray Research at the University of Tokyo, said simply, “Kind of unbelievable!” |