Search for high-energy electron sources with Polar Patrol Balloon

我们利用极地巡逻气球(PPB)进行了长时间的气球飞行，观测到了从10GeV到1TeV的宇宙线电子。2004年1月，在35公里的高空进行了为期13天的观测。PPB-BETTS探测器是一种成像量热计，由闪烁纤维带和插入铅板之间的塑料闪烁体组成。探测器的几何系数约为600 cm·2sr，铅吸收体的总厚度为9个辐射长度。在飞行过程中，成功地开发和运行了使用商业Iridium卫星的新遥测系统、太阳能电池供电和使用CPU的自动液位控制。我们已经收集了5700个100GeV以上的事件，其中包括近100个宇宙射线电子候选者。在这项研究中，我们得到了大气层顶部高于100GeV的宇宙线电子的能谱。用PPB下注得到的能谱与100GeV的外推能谱符合得很好，并且在100GeV-1TeV的统计误差范围内与乳胶室的能谱符合得很好。我们还用PPB-BET观测到了100GeV到1TeV的大气伽马射线。由于高空大气伽马射线主要是由原宇宙射线与大气核的单一相互作用产生的，它们对研究核相互作用模型和大气中微子非常有用。在100GeV到1TeV的能量范围内，观测到的大气伽马射线的数量接近100个事件。我们还用35公里高度的PPB-BET计算了100GeV到1TeV能量范围内的大气伽马能谱。

We have observed cosmic-ray electrons from 10GeV to 1TeV with the PPB-BETS by a long duration balloon flight using Polar Patrol Balloon(PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35km in January 2004. The PPB-BETS detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. The geometrical factor of detector is about 600 cm^2sr and the total thickness of lead absorber is 9 radiation lengths. New telemetry system using a commercial satellite of Iridium, power supply by solar batteries, and automatic level control using CPU have successfully been developed and operated during the flight. We have collected 5700 events over 100GeV including nearly 100 candidates of cosmic-ray electrons. In this study, we derived the energy spectrum of cosmic-ray electrons above 100GeV at the top of atmosphere. The energy spectrum with the PPB-BETS agrees well with the extrapolated spectrum of the BETS at 100GeV, and is consistent with that of the emulsion chambers within statistical errors in the 100GeV-1TeV region. We have also observed atmospheric gamma rays from 100GeV to 1TeV with PPB-BETS. Since atmospheric gamma rays at high altitude are mainly produced by a single interaction of primary cosmic rays with atmospheric nuclei, they are very useful to study nuclear interaction models and atmospheric neutrinos. The number of observed atmospheric gamma rays is neargy 100 events in the energy range of 100GeV to 1TeV. We also derived atmospheric gamma-ray spectrum in the energy range of 100GeV to 1TeV with PPB-BETS at an altitude of 35km.