T. Kajita

Calculation of the flux of atmospheric neutrinos

Atmospheric neutrino-fluxes are calculated over the wide energy range from 30 MeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. The atmospheric muon-flux at high altitude and at sea level is studied to calibrate the neutrino-fluxes at low energies and high energies respectively. The agreement of our calculation with observations is satisfactory. The uncertainty of atmospheric neutrino-fluxes is also studied.

A New calculation of the atmospheric neutrino flux in a 3-dimensional scheme

We have revised the calculation of the flux of atmospheric neutrinos based on a 3-dimensional scheme with the realistic IGRF geomagnetic model. The primary flux model has been revised, based on the AMS and BESS observations, and the interaction model updated to DPMJET-III. With a fast simulation code and computer system, the statistical errors in the Monte Carlo study are negligible. We estimate the total uncertainty of the atmospheric neutrino flux prediction is reduced to

Improvement of low energy atmospheric neutrino flux calculation using the JAM nuclear interaction model

lesssim

Search for Proton Decay via

10 % below 10 GeV. The `3-dimensional effects are found to be almost the same as the study with the dipole magnetic field, but the muon curvature effect remains up to a few 10 GeV for horizontal directions. The uncertainty of the absolute normalization of the atmospheric neutrino is still large above 10 GeV due to the uncertainty of the primary cosmic ray flux above 100 GeV. However, the zenith angle variation is not affected by these uncertainties.

p \rightarrow \nu K^{+}

We present the calculation of the atmospheric neutrino fluxes with an interaction model named JAM, which is used in PHITS (Particle and Heavy-Ion Transport code System) [K. Niita et al., Radiation Measurements 41, 1080 (2006).]. The JAM interaction model agrees with the HARP experiment [H. Collaboration, Astropart. Phys. 30, 124 (2008).] a little better than DPMJET-III[S. Roesler, R. Engel, and J. Ranft, arXiv:hep-ph/0012252.]. After some modifications, it reproduces the muon flux below 1 GeV/c at balloon altitudes better than the modified DPMJET-III, which we used for the calculation of atmospheric neutrino flux in previous works [T. Sanuki, M. Honda, T. Kajita, K. Kasahara, and S. Midorikawa, Phys. Rev. D 75, 043005 (2007).][M. Honda, T. Kajita, K. Kasahara, S. Midorikawa, and T. Sanuki, Phys. Rev. D 75, 043006 (2007).]. Some improvements in the calculation of atmospheric neutrino flux are also reported.

using 260 kiloton

We have searched for proton decay via p→νK+ using Super-Kamiokande data from April 1996 to February 2013, 260 kiloton•year exposure in total. No evidence for this proton decay mode is found. A lower limit of the proton lifetime is set to τ/B(p→νK+)>5.9×1033 years at 90% confidence level.

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We have studied the hadronic interaction for the calculation of the atmospheric neutrino flux by summarizing the accurately measured atmospheric muon flux data and comparing with simulations. We find the atmospheric muon and neutrino fluxes respond to errors in the {pi}-production of the hadronic interaction similarly, and compare the atmospheric muon flux calculated using the HKKM04 [M. Honda, T. Kajita, K. Kasahara, and S. Midorikawa, Phys. Rev. D 70, 043008 (2004).] code with experimental measurements. The {mu}{sup +}+{mu}{sup -} data show good agreement in the 1{approx}30 GeV/c range, but a large disagreement above 30 GeV/c. The {mu}{sup +}/{mu}{sup -} ratio shows sizable differences at lower and higher momenta for opposite directions. As the disagreements are considered to be due to assumptions in the hadronic interaction model, we try to improve it phenomenologically based on the quark parton model. The improved interaction model reproduces the observed muon flux data well. The calculation of the atmospheric neutrino flux will be reported in the following paper [M. Honda et al., Phys. Rev. D 75, 043006 (2007).].

year data of Super-Kamiokande

F. Dufour,1,2 T. Kajita,3, 4 E. Kearns, 1, 4 and K. Okumura3 1Department of Physics, Boston University, Boston, MA 02215 , USA 2Section de Physique, Université de Genève, 1205 Genève, Switzerland 3Research Center for Cosmic Neutrinos, Institute for Cosmic Ray Research (ICRR), University of Tokyo, Kashiwa, Chiba 27 7-8582, Japan 4Institute for the Physics and Mathematics of the Universe (I PMU), University of Tokyo, Kashiwa, Chiba 277-8582, Japan (Dated: January 28, 2010)

Study of cosmic ray interaction model based on atmospheric muons for the neutrino flux calculation

The primary flux model for the calculation of natmospheric neutrino is renewed based on the nAMS02 observation of primary cosmic rays. With nnew cosmic ray spectra model, the interaction nmodel is also studied again, so that it reproduce nthe observed muon flux accurately. Then, we napplied the primary cosmic ray flux model and nthe interaction model to the calculation of natmospheric neutrino flux. In this paper, some of npreliminary results are presented.

Further study of neutrino oscillation with two detectors in Kamioka and Korea

報告番号: 乙14530 ; 学位授与年月日: 2000-01-24 ; 学位の種別: 論文博士 ; 学位の種類: 博士(理学) ; 学位記番号: 第14530号 ; 研究科・専攻: 理学系研究科We have searched for proton decay via p{r_arrow}e{sup +}{pi}{sup 0} using data from a 25.5 kton{center_dot}yr exposure of the Super-Kamiokande detector. We find no candidate events with an expected background induced by atmospheric neutrinos of 0.1thinspthinspevents. From these data, we set a lower limit on the partial lifetime of the proton {tau}/B{sub p{r_arrow}e{sup +}{pi}{sup 0}} to be 1.6{times}10{sup 33} years at a 90{percent} confidence level. {copyright} {ital 1998} {ital The American Physical Society }