臺灣博碩士論文加值系統

摘要
本文是使用日本高能研究室KEKB加速器之BELLE實驗室之數據，來做雙光子物理的e+e-→e+e-γγ→e+e-f2(1270)→e+e-π+π-模式之蒙地卡羅模擬及真實數據分析，由於FEFC可探測電子，故可用於單一偵測事件上，找到系統誤差更低的雙光子部分寬度Γγγ→f2。
我們主要是用atc_pid的訊息來篩選出純的正、負π粒子，並用dEdx vs log10P及TOF mass來觀察其成效。在電子反電子總光輝度5.2fb-1的無偵測實驗數據上，找到峰值1.2346±0.0004GeV/ c2，質量寬度0.167±0.002GeV/ c2的訊號事件323263個，其探測效度為43.86 %，理論上的訊號數目為382400，而在電子反電子總光輝度為4.45fb-1的單一偵測實驗數據上，找到峰值1.24±0.003GeV/ c2，質量寬度0.198±0.01GeV/ c2的訊號事件8179個，而EFC探測器的接收度為14.18%，探測器的探測效度為42.81%，Q2平均為0.86GeV2，form factor為0.407，故理論上的單一偵測事件為7528個。

Abstract
In this thesis,the Monte-Carlo studies and the real data analysis, collected by BELLE laboratory of KEKB accelerator in Japan, of two-photon physics via e+e-→e+e-γγ→e+e-f2(1270)→e+e-π+π-have been presented. The advantage of EFC is that it can be used to tag the two-photon events, and we can get the partial width with less systematic error.
We selected the pions mainly used the ACC-TOF-CDC(atc) package and examined its effects by dEdx vs log10P and TOF mass. We fitted mass at 1.2346±0.0004GeV/c2 with width of 0.167±0.002GeV/c2 for the integrated luminosity 5.2fb-1 of no-tag events, and got 323263 signal events in the analysis of real data. The overall detecting efficiency is 43.86% and the estimated number is 382400. We fitted mass at 1.24±0.003GeV/c2 with width of 0.198±0.01GeV/c2 for the integrated luminosity 4.45fb-1 of single-tag(FEFC-tagged) signal events, and got 8179 signal events in the analysis of real data. The acceptance of the FEFC detector is estimated to be 14.18%, and the total efficiency of the detectors is 42.81%. According the calculation of real data analysis, the average Q2 value is around 0.86GeV2 and the photon form factor which is 0.407 should be include in the cross section calculation. The estimated number is 7528.

目錄
目錄……………………………………………………………………….I
圖形目錄…………………………………………………
第一章緒論……………………………………………………………...1
1.1 光子的性質……………………………………………………..1
1.2 雙光子事件的分類……………………………………………..2
1.3 光子反應的性質………………………………………………..4
第二章理論
2.1 雙光子過程之動力學…………………………………………...5
2.2 由雙光子產生之共振態截面積運算…………………………...6
2.3 e+e-碰撞之雙光子過程的截面積公式與計算………………..…8
2.3.1 共振態f2截面積之計算………………………………….…8
2.3.2 全部產生強子的截面積計算……………………………….10
2.3.3 費米子對產生……………………………………………….11
2.3.4 τ+τ-對的產生…………………………………………….13
第三章實驗室簡介……………………………………………………….15
3.1 加速器簡介……………………………………………………...15
3.2 KEKB之加速器…………………………………………………17
3.3 偵測器的組成………………………………………………...…18
3.3.1 前置量能器EFC(Extreme Forward Calorimeter)………….19
3.3.2 矽頂點偵測器SVD(Silicon Vertex Detector)………………21
3.3.3 中央漂移室CDC(Central wire drift chamber)……………..22
3.3.4 ACC(Aerogel Cerenkov Counter System)…………………..23
3.3.5 飛時計數器TOF(Time-of-Flight Counters)……………….24
3.3.6 電磁量能器ECL(Electromagnetic Calorimetry)…………..25
3.3.7 KL/μ偵測器KLM(KL and Muon Dector)…………………26
3.4 探測器的觸發條件……………………………………………..26
3.4.1 一般觸發條件………………………………………………26
3.4.2 雙光子當訊號的觸發條件…………………………………29
3.4.3 EFC的觸發系統…………………………………………….30
3.4.3.1 觸發訊息種類…………………………………………30
3.4.3.2 EFC的觸發性質………………………………………30
第四章事件模擬與分析…………………………………………………31
4.1 蒙地卡羅模擬分析……………………………………………..31
4.1.1 TREPS……………………………………………………….31
4.1.1.1 輸入的變數……………………………………………32
4.1.1.2 程式……………………………………………………33
4.1.2 蒙地卡羅產生事件…………………………………………33
4.2 EFC探測器的能量沉澱率………………………………………34
4.3 萃取訊號的選取條件…………………………………………..39
4.3.1 基本條件……………………………………………………39
4.3.2 atc_pid的選取條件…………………………………………39
4.3.2.1 atc_pid的意義…………………………………………39
4.3.2.2 atc_pid的分佈圖………………………………………41
4.3.3 CDC的dE/dx vs log10P圖………………………………….49
4.3.4 TOF探測器的粒子質量…………………………………….60
4.3.4.1 正、負軌跡的動量均小於1.2GeV/c…………………61
4.3.4.2 正、負軌跡的動量至少有一個大於1.2GeV/c………75
4.4 共振態的invariant mass…………………………………………80
4.4.1 蒙地卡羅模擬事件………………………………………….80
4.4.2 無偵測事件的invariant mass……………………………….84
4.4.3 單一偵測事件……………………………………………….92
4.4.3.1 有兩個共振態f2(1270)和ρ(770)……………………..93
4.4.3.2 只有一個共振態f2(1270)……………………………..93
4.4.3.3 0.65GeV~0.85GeV和1.15~1.35GeV之invariant mass範圍的基本性質………………………………………….96
4.4.4 其他限制條件……………………………………………..101
4.5 單一偵測事件的Q2值………………………………………...104
第五章結果與討論……………………………………………………..111
5.1 f2(1270)共振態的事件數………………………………………111
5.1.1 單一偵測事件……………………………………………..111
5.1.2 無偵測事件………………………………………………..111
5.2 理論與實驗結果之比較……………………………………….113
5.2.1 單一偵測事件……………………………………………..114
5.2.2 無偵測事件………………………………………………..116
5.3 後緒工作與未來展望………………………………………….117
參考文獻………………………………………………………………….119

參考文獻
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