使用完整重建方法來分析終態為D^(*±) D^∓ π^+ π^-和D^(*+) D^(*-) π^+ π^-的四體反應，兩種分析得到截面積之後，再與二體、三體比較。1.比較直接二體(exclusive two body)、直接三體(exclusive three body)、直接四體(exclusive four body)觀察其截面積變化之規律性；2. 比較vector/pseudoscalar截面積比值如何隨二體、三體、四體的變化；3.觀察D^(*±)生成角度(production angle distribution)，以及在D^(*±)衰變角分佈(Helicity angle distribution)，二體、三體、四體比較分佈的變化，並歸納出D^(*±)可能產生機制。歸納以上述三種的規律性，藉此幫助我們釐清粒子發生過程。
在高能物理分析中，我們使用到蒙地卡羅法(Monte Carlo method)的模擬得出探測器的效率再往回推算真實事件數，或是將模擬的結果和實驗數據做比較，了解分析數據中的物理現象甚至更進一步改善往後的模擬，蒙地卡羅法模擬常用兩種物理模型Pythia與Herwig(KEK使用Pythia模擬)預測粒子的生成情形，我們想知道哪種模型更符合實驗數據，以此為動機研究理解更多粒子生成的機制。 ;We use full reconstruction for analyze 4-body D^(*±) D^∓ π^+ π^- and D^(*+) D^(*-) π^+ π^- events, then compare 2-body, 3-body, 4-body to answer: 1. Exclusive 2-body, exclusive 3-body, exclusive 4-body cross sections and deduce their regularity. 2. How does the vector/pseudoscalar ratio change with the exclusive 2-body, exclusive 3-body, exclusive 4-body processes. 3. Observe the D^* production angle distribution and D^* helicity angle distribution and explain process of production. Answer these questions can help us to clarify production rules and mechanism of particle generation.
In analysis of high energy physics, we use Monte Carlo simulation to get detector efficiency then calculate the number of real events, or compare simulation with real data. In this way we hope to improve future simulations and deeper understanding of its physical phenomenon in analysis. In Monte Carlo simulation, there are two common accepted physics models to predict particle generation, namely Herwig and Pythia (Pythia is adopted in our Belle experiment analysis). Which model is better description for data of Belle experiment, that’s the motivation we want to study “Mechanism of particle generation”.
