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numbers of atmospheric neutrinos would come up from the ground and down from the sky. However, Super-Kamiokande found that while equal numbers of electron neutrinos went up and down, fewer muon neutrinos came up than down. A possible explanation was that muon neutrinos that passed through the earth spent more time traveling than those from the atmosphere, and had more time to change into tau neutrinos, which Super-Kamiokande did not directly detect. Analysis showed that muon neutrinos were oscillating into tau neutrinos.
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324:(Super-K) experiment. In 1991 the Japanese government approved a budget for construction of Super-Kamiokande, and construction began. An underground detector containing 50,000 tons of water, beneath Ikenoyama (Mount Ikeno), it began operation on 1 April 1996. Subsequent work at Super-Kamiokande provided the first definitive experimental evidence for atmospheric
347:(ICRR) at the University of Tokyo. From 1997â2001, Totsuka served as director of ICRR, while continuing as the director of Kamioka Observatory. Following an accident that destroyed over half of the Super-K photomultiplier tubes on 12 November 2001, Totsuka provided key leadership for reconstruction of the detector.
481:
The measurement of neutrino oscillations at a high level of precision was a critical chapter in the history of particle physics. Oscillation arose from the fact that neutrinos had small but finite mass. Neutrino oscillations, and thus the existence of neutrino mass, are not a prediction made by the
473:
The evidence for neutrino oscillation also suggested a possible explanation for the solar neutrino deficit: earlier detectors were not capable of measuring tau and muon neutrinos. The solar electron neutrinos that were predicted to exist but were "missing" from earlier observations might have been
466:, at the Eighteenth International Conference on Neutrino Physics and Astrophysics, in Takayama, Japan. The Super-Kamiokande experiment found evidence for neutrino oscillations through a combination of high-precision measurement and sophisticated statistical modeling of atmospheric neutrino flux.
469:
Neutrino oscillation involves three types of neutrinos, which can convert between types: electron neutrinos, muon neutrinos and tau neutrinos. Atmospheric neutrinos tend to be muon and electron neutrinos, which can pass through the Earth without being absorbed. It was predicted that the similar
273:
Totsuka held the position of research associate at the
University of Tokyo from 1972 to 1979. He was an associate professor of the University of Tokyo from 1979 to 1987, and was promoted to full professor at the University of Tokyo in 1987. From 1972 to 1981 he also worked with the Double Arm
412:. It established strict limits on the proton-decay process, and could detect low-energy neutrinos coming from the Sun as well as atmospheric neutrinos produced by cosmic rays. As a result, Kamioka was one of two locations on Earth to successfully measure the release of neutrinos from a
449:
In addition, the
Kamiokande researchers realized that their data showed a deficit in atmospheric neutrinos that could not be explained away by experimental errors or background neutrino flux. Both atmospheric and solar neutrinos were fewer than the
431:(IMB) detector in the US. As the first detection of neutrinos from beyond the Solar System, the event was hailed as the birth of neutrino astronomy. More than 800 publication have analyzed the data from the Kamioka detector relating to that event.
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and underwent surgery for it in 2000. In 2006, after cancer spread to his lung, he retired from his position at KEK, but served as a director of research at the Japan
Society for the Promotion of Science. Totsuka died on July 10, 2008.
305:. This event, considered to be "the birth of neutrino astronomy", led to the publication of significant results from the Kamioka detector and in 2002 the sharing of a Nobel Prize in Physics between Masatoshi Koshiba and
551:, where he candidly discussed the extent, progress, and treatment of his cancer. Totsuka also revealed an interest in gardening, particularly the flowers in the area where he spent much of his career, in
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of particle physics would predict. Totsuka and his group published the first paper on the atmospheric neutrino anomaly in 1988, a result that would require âas-yet-unaccounted-for physicsâ to explain.
316:(ICRR) at the University of Tokyo from 1988â2002. In 1988, after Masatoshi Koshiba retired, Totsuka took his place as organizer and spokesperson of a core group of researchers to promote an expanded
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Towards the end of his life, Totsuka turned his attention to communicating with the
Japanese public about his illness, science, and culture. He maintained a blog,
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converted from electron neutrinos to tau and muon neutrinos. This was later confirmed through a collaboration between Super-Kamiokande and the
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462:(Super-K) detector, which opened in 1996. In 1998, the Super-Kamiokande collaboration reported the first definitive evidence for atmospheric
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Totsuka was born March 6, 1942, in Fuji, Shizuoka
Prefecture. He completed his B.S. in 1965, his M.S. in 1967 and his Ph.D. in 1972 from the
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446:. The data from Kamiokande crucially confirmed the existence of the solar neutrino problem posed by the work of Davis and Bahcall.
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detector in the United States were able to detect a burst of neutrinos from the explosion of a supernova in the
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was told that if
Totsuka could extend his lifespan by eighteen months, he must receive the prize.
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to establish the
Kamioka Nucleon Decay Experiment. In 1987, both the Kamiokande detector and the
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222:. A leader in the study of solar and atmospheric neutrinos, he was a scientist and director at
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354:(KEK). From 2003â2006, Totsuka served as the director general of KEK where he supervised the
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Among the new research were two major findings from the
Totsuka group. One related to the
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544:(SNO) "for the discovery of neutrino oscillations, which shows that neutrinos have mass".
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365:. From 2006â2008, he served as Director of the Research Center for Science Systems of the
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of particle physics. Indeed, the
Standard Model requires that neutrinos are massless.
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282:(DESY) in Hamburg, Germany. There he investigated electronâpositron collisions.
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Under
Totsuka's leadership, the success of Kamiokande led to the building of the
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In 2015, the evidence provided by the 1998 and 2001 experiments resulted in a
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In addition, as the Director General at KEK, Totsuka successfully oversaw the
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965:"Mourning for Dr. Yoji Totsuka - School of Science, the University of Tokyo"
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744:"Neutrino oscillations: From a historical perspective to the present status"
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328:(1998) and solar neutrino oscillations (2001). This explained the apparent
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1302:"2002 W.K.H. Panofsky Prize in Experimental Particle Physics Recipient"
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1093:"A failed proton decay search accidentally birthed neutrino astronomy"
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902:
401:(Super-K) experiment, Totsuka helped to establish the foundations of
991:"Masatoshi Koshiba, 94, Dies; Nobel Winner Tracked Ghostly Neutrinos"
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was a Japanese physicist and Special University Professor, emeritus,
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on the Kamioka Nucleon Decay Experiment and later as leader of the
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In 1981, Totsuka returned from Germany to Japan to work at the
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427:. The other location to detect the burst of neutrinos was the
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681:"Yoji Totsuka (1942â2008) and the Discovery of Neutrino Mass"
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The Kamioka Nucleon Decay Experiment was designed to detect
500:, exploring differences between matter and antimatter.
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Benjamin Franklin Medal (Franklin Institute) laureates
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From 1995â2002, Totsuka served as the director of the
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Sobel, Henry W.; Suzuki, Yoichiro (1 November 2009).
245:, laying a foundation for the international study of
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293:(ICRR) at the University of Tokyo. He worked with
837:Sobel, Henry W.; Suzuki, Yoichiro (August 2008).
350:From 2002 to 2003, Totsuka was a professor at
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1123:Annual Review of Nuclear and Particle Science
685:Annual Review of Nuclear and Particle Science
352:High Energy Accelerator Research Organization
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1277:"Neutrino 'flip' wins physics Nobel Prize"
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309:for the detection of cosmic neutrinos.
969:School of Science, University of Tokyo
1119:"The Scientific Life of John Bahcall"
1071:NNN08, Paris, France, September, 2008
989:Overbye, Dennis (November 16, 2020).
7:
438:. Solar neutrinos were detected by
312:Totsuka was a full professor in the
356:K2K neutrino-oscillation experiment
1153:10.1146/annurev.nucl.010909.083722
705:10.1146/annurev.nucl.010909.083832
566:Benjamin Franklin Medal in Physics
14:
1275:Webb, Jonathan (6 October 2015).
1256:"The Nobel Prize in Physics 2015"
1191:"The Super-Kamiokande experiment"
1189:Suzuki, Yoichiro (2 April 2019).
1091:Siegel, Ethan (October 6, 2022).
963:Komamiya, Sachio (Aug 19, 2008).
345:Institute for Cosmic Ray Research
332:and established the existence of
314:Institute for Cosmic Ray Research
291:Institute for Cosmic Ray Research
1117:Haxton, Wick (1 November 2009).
389:Working with Nobel prize winner
216:, March 6, 1942 â July 10, 2008)
1375:People from Shizuoka Prefecture
1195:The European Physical Journal C
901:Kajita, Takaaki (1 July 2009).
778:10.1016/j.nuclphysb.2016.01.025
1216:10.1140/epjc/s10052-019-6796-2
280:Deutsches Electron Synchrotron
1:
1380:Winners of the Panofsky Prize
1355:Deaths from colorectal cancer
604:American Astronomical Society
542:Sudbury Neutrino Observatory
534:Super-Kamiokande Observatory
476:Sudbury Neutrino Observatory
178:Clarivate Citation Laureates
742:Bilenky, S. (1 July 2016).
508:Totsuka was diagnosed with
237:Totsuka helped to discover
212:
1411:
1370:University of Tokyo alumni
1064:"Memories of Yoji Totsuka"
839:"Yoji Totsuka (1942â2008)"
639:Katsuhiko Sato (physicist)
429:IrvineâMichiganâBrookhaven
299:IrvineâMichiganâBrookhaven
1306:American Physical Society
588:European Physical Society
206:
154:Franklin Institute Awards
37:
28:
1385:Directors General of KEK
274:Spectrometer (DASP) and
1330:The Fourth Three-Months
594:Inoue Prize for Science
549:The Fourth Three-Months
526:Nobel Prize for Physics
261:under the direction of
1043:The Franklin Institute
611:Nishina Memorial Prize
436:solar neutrino deficit
425:Large Magellanic Cloud
386:
330:solar neutrino deficit
303:Large Magellanic Cloud
276:JADE particle detector
172:Nishina Memorial Prize
464:neutrino oscillations
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326:neutrino oscillations
239:neutrino oscillation
1360:Japanese physicists
1207:2019EPJC...79..298S
1145:2009ARNPS..59....1H
919:2009PhT....62g..65K
770:2016NuPhB.908....2B
697:2009ARNPS..59...41S
395:Kamioka Observatory
341:Kamioka Observatory
287:Kamioka Observatory
259:University of Tokyo
224:Kamioka Observatory
220:University of Tokyo
124:University of Tokyo
114:Kamioka Observatory
80:University of Tokyo
995:The New York Times
517:winning physicist
387:
318:Cherenkov detector
60:10 July 2008
45:6 March 1942
16:Japanese physicist
928:10.1063/1.3177237
748:Nuclear Physics B
629:Masatoshi Koshiba
600:Bruno Rossi Prize
584:EPS Special Prize
519:Masatoshi Koshiba
510:colorectal cancer
498:B-meson "factory"
440:Raymond Davis Jr.
416:source, when the
391:Masatoshi Koshiba
383:Michael Witherell
307:Raymond Davis Jr.
295:Masatoshi Koshiba
263:Masatoshi Koshiba
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1039:"Yoji Totsuka"
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213:Totsuka YĹji
201:Yoji Totsuka
200:
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23:Yoji Totsuka
1350:2008 deaths
1345:1942 births
1129:(1): 1â20.
617:Asahi Prize
559:Recognition
528:, given to
515:Nobel Prize
160:Asahi Prize
1339:Categories
1261:2020-02-16
1201:(4): 298.
761:1602.00170
645:References
414:cosmogenic
253:Early life
1286:6 October
1233:254110636
1225:1434-6052
1161:0163-8998
1136:0904.2865
1097:Big Think
1003:0362-4331
937:0031-9228
881:205040545
865:1476-4687
794:119220135
786:0550-3213
713:0163-8998
540:from the
532:from the
418:supernova
405:physics.
397:and the
363:B-factory
358:and the
247:neutrinos
68:(aged 66)
1311:10 March
1281:BBC News
1169:15314700
873:18719580
799:10 March
754:: 2â13.
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