New Developments of Accelerator Neutrino Experiments

在本研究中，我们完成了世界上第一个长基线中微子振荡（LBNO）实验K2 K，在KEK和神冈之间的基线距离为250 km，（2）计划利用正在建设的东海JHF高强度质子同步加速器进行下一代LBNO实验;（3）在日本进行了一个中微子工厂的可行性研究，关于第（1）项，我们已经报道了相当于我们目标（定义为10^质子输送到生产靶上）的大约一半的积分束流强度的数据<20>。这一结果与Super-Kamiokande合作组通过大气中微子观测发现的ν μ→ν τ振荡一致。统计波动伪造这些结果的概率小于1%。K2 K实验将于2005年3月底完成。关于第（2）项，我们已经准备了从东海到神冈295 km的下一代LBNO实验的意向书。意向书由来自12个国家的约150名物理学家签署，并由这个国际团队提交给JHF总部。关于第（3）项，我们提出了一个独特的日本中微子工厂方案，该方案基于FFAG（固定场交变梯度）加速器和μ子储存环。这部戏剧吸引了全世界的兴趣。我们已经提交了详细的研究报告，目前150 MeV FFAG的研发正在进行中。我们还向JHF总部提交了一份意向书，建议利用JHF高强度质子同步加速器作为未来的μ子源，以实现基于FFAG的中微子工厂的想法。

In this research, we have (1) conducted the world first long baseline neutrino oscillation (LBNO) experiment, K2K, with a baseline distance of 250 km between KEK and Kamioka ; (2) made planning of a next generation LBNO experiment utilizing the JHF high intensity proton synchrotron under construction at Tokai ; and (3) made a feasibility study of a neutrino factory, future high-intensity neutrino source, in Japan.Concerning item (1), we have reported the data corresponding to the integrated beam intensity of about half of our goal (defined as 10^<20> protons delivered onto the production target). The results are consistent with ν_μ→ν_τ oscillation discovered by the Super-Kamiokande Collaboration through observations of atmospheric neutrinos. The probability that statistical fluctuations fake these results is less than 1 %. The K2K experiment will reach the goal by the end of March, 2005.Concerning item (2), we have prepared an LOI (letter of intent) of the next generation LBNO experiment from Tokai to Kamioka with a distance of 295 km. The LOI was signed by about 150 physicists from 12countries, and wassubmitted by this international team to the JHF headquarters. A sort of pre-Program Advisory Committee reviewed this LOI and recommended early realization of the experiment, recognizing its very high priority.Concerning item (3), we have proposed a unique Japanese scheme for a neutrino factory, based on FFAG (Fixed-Field Altenating Gradient) accelerators and a muon storage ring. This scherme attracted worldwide interests. We have presented a detailed study report, and currently an R&D of 150 MeV FFAG is underway. We have also submitted an LOI to the JHF headquarters, proposing the utilization of the JHF high-intensity proton synchrotron as a future muon source to realize this idea of the FFAG-based neutrino factory.