NAKAYA Tsuyoshi Kyoto University, Faculty of Science, Associate Professor, 大学院・理学研究科, 助教授 (50314175)
YOKOYAMA Masashi Kyoto University, Faculty of Science, Research Associate, 大学院・理学研究科, 助手 (90362441)
KOBAYASHI Takashi High Energy Accelerator Research Organization, Institute of Particle and Nuclear Studies, Associate Professor, 素粒子原子核研究所, 助教授 (70291317)
|Budget Amount *help
¥126,880,000 (Direct Cost: ¥97,600,000、Indirect Cost: ¥29,280,000)
Fiscal Year 2005: ¥6,890,000 (Direct Cost: ¥5,300,000、Indirect Cost: ¥1,590,000)
Fiscal Year 2004: ¥7,020,000 (Direct Cost: ¥5,400,000、Indirect Cost: ¥1,620,000)
Fiscal Year 2003: ¥28,860,000 (Direct Cost: ¥22,200,000、Indirect Cost: ¥6,660,000)
Fiscal Year 2002: ¥60,710,000 (Direct Cost: ¥46,700,000、Indirect Cost: ¥14,010,000)
Fiscal Year 2001: ¥23,400,000 (Direct Cost: ¥18,000,000、Indirect Cost: ¥5,400,000)
We measure muon neutrino oscillation in the K2K experiment, the KEK to Kamioka long-baseline neutrino oscillation experiment. One hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of 158.1 events without oscillation. A distortion of the energy spectrum is also observed in 58 single-ring muon-like events with reconstructed energies. The probability that the observations are explained by a statistical fluctuation with no neutrino oscillation is 0.0015%. In a two flavor oscillation scenario, the allowed region of mass squared difference at the maximum oscillation is between 0.0019 and 0.0035 eV^2 at the 90% confidence level with a best-fit value of 0.0028 eV^2.
Thus, the K2K experiment confirm neutrino oscillation discovered in the Super-Kamiokande atmospheric neutrino observation.
We also search for electron neutrino appearance and set the upper limit of 0.13 for sin2^2θ_<μe> at Δm^2=2.8×10^<-3>eV^2.