Study on chemical composition of primary cosmic rays with energies above 10^<16> eV

本研究的目的是获得能量在10 TeV以上的初级宇宙线的化学成分信息。自2000年8月以来，在玻利维亚的查卡尔塔亚。1999年，我们进行了研究，以获得最适合用于化学成分测定的参数，并估计了测定的准确度。在此过程中，我们使用CORSIKA代码来模拟空气淋浴。因此，我们确认能够通过测量空气切伦科夫光的横向分布和到达时间分布来确定成分。然后我们开始建造探测器，直到1999年底。2000年4月，我们将这些设备运到玻利维亚，并在Mt.查卡尔塔亚该行动于2000年8月开始，观察到的数据被转移到日本。在日本和玻利维亚同时进行了分析。初步结果表明，观测到的化学成分与直接测量结果非常一致。这是一个至关重要的结果，因为这种一致性保证了我们的测量方法在更高能量范围内应用的正确性。我们将再观察三年，然后得出最终结果。

The purpose of this research is to get information on the chemical composition of primary cosmic rays with energies above 10 TeV.For this we have observed air cherenkov light at MAS array on Mt. Chacaltaya in Bolivia since August 2000. In 1999 we examined to get the most suitable parameter for use of determination of the chemical composition and to estimate the accuracy in the determination. In this procedure, we used CORSIKA code to simulate air showers. As a result, we confirmed to be able to determine the composition by measuring both the lateral distributions and the arrival time distributions of air Cherenkov light. Then we started to construct detectors up to the end of 1999. In April 2000, we ship these equipments to Bolivia and installed these in MAS array at Mt. Chacaltaya. The operation was started in August 2000 and the observed data was transferred to Japan. The analysis has been made simultaneously in Japan and in Bolivia. The preliminary result shows that observed chemical composition is much consistent with those obtained with direct measurements. This is a crucially important result because this consistency guarantee the rightness to apply our measuring method in more high energy range. We are going to make the observation for more three years and will get the final result.