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Fast Breaking Comments

By Takaaki Kajita

ESI Special Topics, August 2005
Citing URL - http://www.esi-topics.com/fbp/2005/august05-TakaakiKajita.html

Takaaki Kajita answers a few questions about this month's fast breaking paper in the field of Physics.

From •>>August 2005  

Field: Physics
 Article Title: Evidence for an oscillatory signature in atmospheric neutrino oscillations - art. no. 101801
 Authors: Ashie, Y;Hosaka, J;Ishihara, K;Itow, Y;Kameda, J;Koshio, Y;Minamino, A;Mitsuda, C;Miura, M;Moriyama, S;Nakahata, M;Namba, T;Nambu, R;Obayashi, Y;Shiozawa, M;Suzuki, Y;Takeuchi, Y;Taki, K;Yamada, S;Ishitsuka, M;Kajita, T;Kaneyuki, K;Nakayama, S;Okada, A;Okumura, K;Ooyabu, T;Saji, C;Takenaga, Y;Desai, S;Kearns, E;Likhoded, S;Stone, JL;Sulak, LR;Walter, CW;Wang, W;Goldhaber, M;Casper, D;Cravens, JP;Gajewski, W;Kropp, WR;Liu, DW;Mine, S;Smy, MB;Sobel, HW;Sterner, CW;Vagins, MR;Ganezer, KS;Hill, J;Keig, WE;Jang, JS;Kim, JY;Lim, IT;Ellsworth, RW;Tasaka, S;Guillian, G;Kibayashi, A;Learned, JG;Matsuno, S;Takemori, D;Messier, MD;Hayato, Y;Ichikawa, AK;Ishida, T;Ishii, T;Iwashita, T;Kobayashi, T;Maruyama, T;Nakamura, K;Nitta, K;Oyama, Y;Sakuda, M;Totsuka, Y;Suzuki, AT;Hasegawa, M;Hayashi, K;Inagaki, T;Kato, I;Maesaka, H;Morita, T;Nakaya, T;Nishikawa, K;Sasaki, T;Ueda, S;Yamamoto, S;Haines, TJ;Dazeley, S;Hatakeyama, S;Svoboda, R;Blaufuss, E;Goodman, JA;Sullivan, GW;Turcan, D;Scholberg, K;Habig, A;Fukuda, Y;Jung, CK;Kato, T;Kobayashi, K;Malek, M;Mauger, C;McGrew, C;Sarrat, A;Sharkey, E;Yanagisawa, C;Toshito, T;Miyano, K;Tamura, N;Ishii, J;Kuno, Y;Nagashima, Y;Takita, M;Yoshida, M;Kim, SB;Yoo, J;Okazawa, H;Ishizuka, T;Choi, Y;Seo, HK;Gando, Y;Hasegawa, T;Inoue, K;Shirai, J;Suzuki, A;Koshiba, M;Nakajima, Y;Nishijima, K;Harada, T;Ishino, H;Nishimura, R;Watanabe, Y;Kielczewska, D;Zalipska, J;Berns, HG;Gran, R;Shiraishi, KK;Stachyra, A;Washburn, K;Wilkes, RJ
Journal: PHYS REV LETT
Volume: 9310
Page: 1801-1801
Year: SEP 3 2004
* Univ Tokyo, Inst Cosm Ray Res, Kamioka Observ, Gifu 5061205, Japan.
* Univ Tokyo, Inst Cosm Ray Res, Kamioka Observ, Gifu 5061205, Japan.
* Univ Tokyo, Inst Cosm Ray Res, Res Ctr Cosm Neutrinos, Chiba 2778582, Japan.
* Boston Univ, Dept Phys, Boston, MA 02215 USA.
* Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA.
* Univ Calif Irvine, Dept Phys & Astron, Irvine, CA 92697 USA.
* Calif State Univ Dominguez Hills, Dept Phys, Carson, CA 90747 USA.
* Chonnam Natl Univ, Dept Phys, Kwangju 500757, South Korea.
* George Mason Univ, Dept Phys, Fairfax, VA 22030 USA.
* Gifu Univ, Dept Phys, Gifu 5011193, Japan.
* Univ Hawaii, Dept Phys & Astron, Honolulu, HI 96822 USA.
* Indiana Univ, Dept Phys, Bloomington, IN 47405 USA.
* High Energy Accelerator Res Org KEK, Tsukuba, Ibaraki 3050801, Japan.
* Kobe Univ, Dept Phys, Kobe, Hyogo 6578501, Japan.
* Kyoto Univ, Dept Phys, Kyoto 6068502, Japan.
* Los Alamos Natl Lab, Div Phys, Los Alamos, NM 87544 USA.
* Louisiana State Univ, Dept Phys & Astron, Baton Rouge, LA 70803 USA.
* Univ Maryland, Dept Phys, College Pk, MD 20742 USA.
* MIT, Dept Phys, Cambridge, MA 02139 USA.
* Univ Minnesota, Dept Phys, Duluth, MN 55812 USA.
* Miyagi Univ Educ, Dept Phys, Sendai, Miyagi 9800845, Japan.
* SUNY Stony Brook, Dept Phys & Astron, Stony Brook, NY 11794 USA.
* Nagoya Univ, Dept Phys, Aichi 4648602, Japan.
* Niigata Univ, Dept Phys, Niigata 9502181, Japan.
* Osaka Univ, Dept Phys, Osaka 5600043, Japan.
* Seoul Natl Univ, Dept Phys, Seoul 151742, South Korea.
* Shizuoka Seika Coll, Shizuoka 4258611, Japan.
* Univ Shizuoka, Dept Syst Engn, Shizuoka 4328561, Japan.
* Sungkyunkwan Univ, Dept Phys, Suwon 440746, South Korea.
* Tohoku Univ, Res Ctr Neutrino Sci, Sendai, Miyagi 9808578, Japan.
* Univ Tokyo, Tokyo 1130033, Japan.
* Tokai Univ, Dept Phys, Kanagawa 2591292, Japan.
* Tokyo Inst Technol, Dept Phys, Meguro Ku, Tokyo 1528551, Japan.
* Univ Warsaw, Inst Expt Phys, PL-00681 Warsaw, Poland.
* Univ Washington, Dept Phys, Seattle, WA 98195 USA.

ST:  Why do you think your paper is highly cited?

Many members of Super-Kamiokande taken at the top of the Super-Kamiokande detector.
“In this paper, we have shown for the first time that the neutrino changes its flavor with the sinusoidal function as predicted by neutrino oscillations.”

Click for larger view of group image.

Flavor is a quantum number of elementary particles related to their weak interactions. There are three kinds (three flavors) of neutrinos. These are called electron-neutrinos, muon-neutrinos and tau-neutrinos. Quantum theory requires that if neutrinos change flavor they must have mass. These small but finite neutrino masses are believed to be related to the extremely high energy physics that cannot be studied directly by acclerator experiments. Therefore the study of neutrino masses is very important. In 1998, we—the Super-Kamiokande collaboration—had already shown that neutrinos change flavor through a study of atmospheric neutrinos. This discovery was essentially accepted as evidence for neutrino oscillations—neutrino oscillation refers to the phenomenon of neutrinos oscillating between different flavors, in the sense that the flavor eigenstates are defined as the wavefunction that will produce a charged lepton of a particular type (electron, muon, or tau lepton) when interacting with a nucleon, and a neutrino produced as one of these eigenstates will behave as a superposition of different flavor eigenstates with the ratio of proportions varying periodically. However, since then, there have been several new theoretical proposals that could explain the observed data without the existence of neutrino oscillations. Therefore, it has been regarded that a final confirmation of neutrino oscillations should be made. This paper excluded these alternative models, making a final confirmation of neutrino oscillations. It is primarily for this reason that we think this paper is highly cited.

ST:  Does it describe a new discovery or a new methodology that's useful to others?

In this paper, we have shown for the first time that the neutrino changes its flavor with the sinusoidal function as predicted by neutrino oscillations. This is the final confirmation that the neutrino changes its flavor by neutrino oscillations generated by neutrino masses. We believe that many long-baseline neutrino oscillation experiments will be carried out in the near future. These experiments will study neutrino oscillations in substantially more detail.

ST:  How did you become involved in this research?

The advent of the Super-Kamiokande detector under Mount Ikena in the Japanese Alps in 1996 revolutionized the experimental study of atmospheric and solar neutrinos. Prior to this time there had been interesting data that suggested the existence of neutrino oscillations through the study of atmospheric neutrinos in large underground detectors. Therefore, from the very beginning of the Super-Kamiokande experiment, the study of atmospheric neutrinos has been one of the main topics in this experiment.End

Professor Takaaki Kajita
Institute for Cosmic Ray Research
University of Tokyo
Tokyo, Japan

ESI Special Topics, August 2005
Citing URL - http://www.esi-topics.com/fbp/2005/august05-TakaakiKajita.html

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