量測宇宙線渺子在大亞灣探測器的能量損耗

Abstract

大亞灣反應堆微中子實驗的主要目的是利用核反應堆產生的電子反微中子 來量測微中子混合角\theta_13。而宇宙線渺子通過大亞灣探測器時，會與探測器的物質交互作用，並產生大亞灣實驗中主要的背景來源。因此，我們感興趣的是宇宙線渺子在大亞灣探測器中的物理現象。本論文研究了宇宙線渺子在通過大亞灣探測器時的能量損失行為，我們發現由於大亞灣探測器大小的限制，所以探測器無法吸收渺子沉積在探測器內的所有能量，而產生能量洩漏效應。這種能量洩漏效應造成了能量損失分佈有一低能量尾巴出現。為了減少這種能量洩漏效應，我們引入了基準體積的選擇條件。引入基準體積的選擇條件後，利用朗道分佈函數擬合後的結果得到明顯的改善，並且在三個實驗大廳的平均能量損失分別為2.977_{−0.332}^{+0.093}、3.275_{−0.332}^{+0.093}和 3.183_{−0.332}^{+0.093}，單位是MeV cm2 g-1。

The main task of the Daya Bay reactor neutrino experiment is to measure the neutrino mixing angle \theta_13. However, the cosmic ray muon could induce important backgrounds to Daya Bay experiment. Thus it is of interests to study muon physics with Daya Bay detectors. In this thesis, we focus on the phenomenon of muon energy loss. Because the limit on the detector size , muon energy cannot be completely absorbed by the detector. This energy leakage effect causes the low energy tail in the spectrum of muon deposit energy. To reduce the energy leakage effect, we apply fiducial volume cut in our measurement. After applying the fiducial volume cut, the quality of the fit are significantly improved by fitting with the Landau distribution function. The mean rates of muon energy loss in a unit of MeV cm2 g-1 at Daya Bay experiment are: 2.977_{−0.332}^{+0.093}、3.275_{−0.332}^{+0.093}, and 3.183_{−0.332}^{+0.093} in 3 experimental halls 1, 2, and 3, respectively.