基本情報

所属
東北大学 ニュートリノ科学研究センター 教授
学位
理学博士(東京工業大学)

J-GLOBAL ID
200901045007903369

外部リンク

1983: As a doctor course student, I joined VENUS e+e- colliding beam experiment at TRISTAN. I stayed at KEK as an entrusted student from Tokyo Inst. Tech. throughout my DC student period. I was involved in the central drift chamber (CDC) subgroup. My ph.D thesis showed that the top quark was heavier than 24GeV.

1987: I obtained a job at KEK and joined KL --> mu + e rare decay search experiment. I was in charge of e/pi/mu particle identification system. Unfortunately, KL --> mu + e decay was not observed but KL --> mu + mu branching ratio was measured with the best precision at that time.

1989: I moved to Tohoku Univ. and joined the SLD e+e- colliding beam experiment at SLAC to study Z0 boson. I stayed at SLAC as a visiting researcher for about half of my time for about 6 years period. At SLAC, I was involved in the VXD3 and CRID sub detector groups. For VXD3, I designed a cluster processor algorithm and implemented it in, then becoming popular, a XILINX FPGA. VXD3 can identify b, c-quarks using the vertex displacement and CRID can separate s-s_bar events from u/d quark events through leading K/pi particle separation. With these strong quark ID capability and polarized beam, SLD could measure asymmetry of Fermion-Z0 couplings and therefore, the weak mixing angle, Theta_W, precisely.
I also did an accounting job of US/Japan cooperation fund staying at SLAC. I learned how to handle piles of receipts from this experience.

Around 1996, I returned to Tohoku Univ. and became a starting member of the KamLAND experiment. KamLAND measured the reactor antineutrinos coming from several nuclear reactors hundreds of kilometers away and identified the second neutrino oscillation. I was in charge of the 1kton liquid scintillator (LS), and LS container: 13m diameter transparent plastic balloon, etc. etc. The construction of the KamLAND detector finished in 2001. The detector is still now the largest homogeneous LS detector in the world. For me, it was a big jump from 10g vertex detector CCD to kilo tons of liquid scintillation detector, from fine electronics to brute hydraulics to deal, from above-ground accelerator lab. to a deep underground lab. and, from physics of 91GeV Z0 to possibly milli-eV neutrinos.
In 2002, KamLAND announced the detection of the reactor neutrino deficit and later clean oscillation pattern. I received the first Koshiba prize with my two colleagues in 2004.
The sensitivity of the KamLAND detector turned out to be good enough to detect the geo-neutrinos whose energy and flux are much smaller than the reactor neutrinos. KamLAND measured the geo-neutrino for the first time in the world and the result was published in Nature in 2005. In 2015, the initial KamLAND group was awarded Breakthrough Prize.

KamLAND showed that the neutrino oscillation parameters, Theta12 and Dm12 are not so small. This means there is possibility to measure leptonic CP violation by neutrino oscillations in the future, IF another neutrino mixing angle Theta13 is not so small. Then detecting finite Theta13 became next very important subject. I and theorists wrote a paper in 2003 and showed that reactor measurement of direct theta13 at a baseline ~1.5km, is effective to reduce the ambiguities of the future accelerator measurement of CP violation. Then we formed a reactor-Theta13 experiment, KASKA, which was supposed to use the world largest Kashiwazaki-Kariwa nuclear power station. However, unfortunately the KASKA was not supported in the end.
In 2006, the KASKA group joined French reactor-Theta13 project, Double Chooz (DC). DCJapan budget was approved by JSPS as the category of special promotion of Grant-in-Aid for scientific research(特別推進). DCJapan group took responsibility of the photomultipliers, light calibration and data acquisition monitor systems and analysis. The detector construction was complete in the end of 2010. In Nov. 2011, the DC group reported an indication of a not-so-small Theta13 for the first time using reactor neutrinos. In the fall of 2014, the construction of the DC near detector was complete. In 2019, the new Theta13 result obtained using near-far detectors were uploaded to arXive.
In these days the Theta13 measured by reactor neutrino experiments (DC, DayaBay, RENO) are used to enhance the sensitivity of CP violation in accelerator experiments (T2K, Nova) as expected back to 16 years ago.

Together with the academic studies, I am performing R&D for the reactor operation monitor by neutrinos for the safe guard purpose. By monitoring the reactor neutrinos, it is possible to know the plutonium production in the reactor fuel. The reactor neutrino monitor is one of the candidates of the novel technology program of IAEA.

In July 2016, I was selected as a Blaise Pascal Chair of French for subject of "Promotion of Neutrino Science". From April 2017, till Aug. 2018, I stayed at APC Lab., France and performed many seminars, lectures, Double Chooz experiment, R&D of novel neutrino detector technology: LiquidO, and writing a text book.

Now, I am involved in the sterile neutrino experiment JSNS2 at the MLF beam line of the JPARC accelerator complex. This experiment direct-tests the LSND result with much improved performances. I have contributed measurements of Theta_W, Theta12, Dm12, Theta13 and am hoping to detect (Theta14, Dm41) next, by JSNS2 experiment.

Near future: I am planning to improve the sensitivity of JSNS2 experiment. Also I am trying resuming R&D of LiquidO technology after coming back from France. Also I am studying possible use of decay at rest neutrinos.

In 2010, we(3) translated an English text book to Japanese (素粒子・原子核物理学の基礎) and it was printed In May 2011 (just after the Tohoku disaster) from Kyoritsu publishing company.
In 2015, I wrote a book "Neutrino Oscillations: A practical guide to basics and applications" as Springer lecture series. I am glad this book is being continuously sold well.
In 2017. we(4) wrote a Japanese book "現代素粒子物理" from Morikita publishing company.
I enjoy writing text book because I can learn a lot from doing so.
I am interested in teaching intuitive physics.

論文

  163

MISC

  142

書籍等出版物

  3

講演・口頭発表等

  87

社会貢献活動

  49

メディア報道

  12