Precise Determination of Atmospheric Neutrino Flux

为了测量大气中微子的绝对通量，开展了以下研究工作：（1）研制和建造了簇射计数器系统和气凝胶切伦科夫计数器系统，以提高BESS超导谱仪的粒子识别能力。(2)A 1995年夏天在加拿大北方进行了一次球载实验，测量初级宇宙线的光谱。获得了0.4 ~ 100 GeV能区的质子能谱，估计系统精度为10%。还清楚地观察到太阳调制的效果。（3）分别于1995年冬和1996年夏在日本和加拿大北方进行了宇宙线μ子谱的测量。宇宙线μ介子能谱的动量范围为0.4和100 GeV/c之间的系统精度为2%。(4)A研制了初级宇宙线与大气相互作用的模拟程序。

In order to determine the absolute flux of the atmospheric neutrinos, the following studies were carried out :(1)A shower counter system and an Aerogel Cherenkov counter system were developed and constructed to improve the particle identification capability of the BESS superconducting spectrometer.(2)A balloon-borne experiment was carried out in the summer, 1995 in northern Canada to measure spectra of primary cosmic rays. Energy spectrum of protons in the energy region from 0.4 to 100 GeV was obtained with an estimated systematic accuracy of 10%. The effect of solar modulation was also clearly observed.(3)Measurements of cosmic ray muon spectrum were performed in Japan and northern Canada in the winter, 1995, and the summer, 1996, respectively. Cosmic ray muon energy spectra in the momentum range between 0.4 and 100 GeV/c were obtained with a systematic accuracy of 2%.(4)A simulation program for interactions between primary cosmic rays and the air has been developed.