分析ANITA-II之數據以搜尋極高能宇宙微中子

Abstract

南極瞬間脈衝天線陣列(ANITA)是一個以南極冰層為目標，搜尋極高能宇宙微中子的長程氣球實驗。在已發表的分析結果中，ANITA已經發現了18個高能宇宙射線事件以及1個可能的微中子事件。利用廣大的有效視野，ANITA是當前能夠探測最低通量的極高能微中子實驗。然而，這個南極的氣球實驗被為數眾多的人為訊號干擾，以至於在分析上有著不可避免的人為雜訊背景。在這篇論文中，我們討論在介質中由微中子和原子反應所產生的切倫可夫輻射所帶有的極性特質，以及討論運用這項特質來更深入探討蒐集到的實驗數據。我們說明在汽球實驗獨特的幾何架構下的切倫可夫輻射極性，並以這項特性降低更多來自人為訊號的不確定性。

Antarctic Impulse Transient Antenna (ANITA) is a balloon experiment searching for the Askaryan effect of ultrahigh energy neutrino-nucleon interactions in the Antarctic ice. ANITA has published its result with one possible neutrino candidate and 18 UHE cosmic ray events. It is also the experiment that has set the lowest neutrino flux upper limit because of the largeness of its effective field of view. However, ANITA triggering system was seriously interfered by the ground anthropogenic noises so that the analysis was compromised by an irreducible anthropogenic background. In this thesis, we demonstrate that the Cherenkov radiation that is induced by neutrino-nucleon interaction in the ice should have a unique polarity and can be used as a characteristic to help us looking further into the data. In our analysis, we point out the unique character of the neutrino polarity under the specific geometry in the ANITA experiment and demonstrate the reduction of anthropogenic background in data analysis by invoking this unique character.