报告题目：1) Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the ISS

　　报告摘要：Precision measurements by AMS of fluxes and flux ratios of charged elementary particles in cosmic rays are presented. In the absolute rigidity range ～60 to ～500 GV, the antiproton, proton, and positron fluxes are found to have nearly identical rigidity dependence while the electron flux exhibits a different rigidity dependence. Below 60 GV, the antiproton-to-proton, antiproton-to-positron, and proton-to-positron flux ratios each reach a maximum. From ～60 to ～500 GV, these flux ratios show no rigidity dependence. These are new and unexpected observations of the properties of elementary particles in the cosmos

　　报告题目：2) 3-dimensional Reconstruction of Electron and Positron Showers in AMS ECAL

　　报告摘要：The Alpha Magnetic Spectrometer, AMS, is successfully collecting data on the International Space Station since its installation on May 19, 2011. One of the main objectives of AMS is the precision measurement of high energy cosmic ray electrons and positrons. The key detector for this measurement is the Electromagnetic Calorimeter. Reconstruction of electrons and positrons in the calorimeter uses a 3-dimensional shower parametrization, which accounts for the detector specifics: finite size of the calorimeter, non-uniform efficiency of the signal collection, and saturation effects due to the electronics and due to high energy density in the active calorimeter elements. This technique provides AMS with a precision energy measurement of electrons and positrons up to several TeV as well as an excellent rejection of the proton background.

　　报告人：许伟伟 （麻省理工学院）

　　报告人简介：许伟伟，2009年毕业于南开大学物理学院，2014年在中科院高能所获得博士学位，自2014年起在麻省理工学院（MIT）做博士后研究。自2010年起，在由丁肇中教授领导的阿尔法磁谱仪（AMS）实验，从事电磁量能器的刻度和重建，以及宇宙线电子、正电子和反质子等的物理分析。

　　报告时间：2017年7月24日（星期一）15:00

　　报告地点：紫台大楼517会议室

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　　紫金山天文台学术委员会