Study of the Origin of the Cosmic-Ray Antiprotons using the BESS Spectrometer

为了研究宇宙射线反质子的起源，在1999年和2000年，利用BESS超导光谱仪进行了两次连续的气球实验，以精确测量太阳极大期宇宙射线的光谱。在这些飞行中，积累了一千多个反质子事件。通过这些飞行数据，我们清楚地观察到电荷对太阳调制的依赖性，这是了解次级反质子能谱的必然结果。在原宇宙射线中对反氦核进行了搜索，并提出了反氦核与氦核之比的上限小于7×10^<-7>，这是世界上最严格的。测量了初级质子的能谱，特别是在1 GeV以下的低能区。利用气球发射期间的数据，观测到残余压力与质子谱的关系，以便检验宇宙射线在大气中发展的模型。举办了7^< > BESS研讨会，以评估过去BESS实验的结果。为了进一步研究低能反质子的主要来源，在该研讨会上讨论并计划在南极洲进行长时间飞行，用较小的超导光谱仪进行更长时间的气球载实验。

In order to study the origin of the cosmic-ray antiprotons,1. Two successive balloon-borne experiments with the BESS superconducting spectrometer have been carried out in 1999 and 2000 to measure precise spectrum of the cosmic rays at the solar maximum period. In these flights, more than thousand antiproton events were accumulated.2. By the data from those flights, charge dependence on the solar modulation was clearly observed, which is inevitable to understand the energy spectrum of secondary antiprotons.3. A search for antihelium nuclei in the primary cosmic rays has been carried out and an upper limit of the ratio of antiheliums to helium nuclei to be less than 7×10^<-7> was placed, which is most stringent in the world.4. Precise energy spectrum of primary protons was measured, especially in low energy region below 1 GeV.Using the data during the acsend of the balloon, residual pressure dependence on the proton spectrum was observed in order to check models of the development of cosmic rays in the atmosphere.5. The 7^<th> BESS workshop was held to evaluate the results from past BESS experiments. For further investigation of the primary origin of the low energy antiprotons, a longer balloon-borne experiment with smaller superconducting spectrometer was discussed and planed by a long duration flight in Antarctica in that workshop.