B介子的稀有衰變至Rho Pi及Rho K之研究｜國立清華大學博碩士論文庫

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研究生：	趙元 Chao, Yuan
論文名稱：	B介子的稀有衰變至Rho Pi及Rho K之研究 Measurment of Charmless Hadronic Rare Decay B^0 to Rho h at BELLE
指導教授：	耿朝強 Geng,Chao-Qiang
口試委員:
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2001
畢業學年度：	89
語文別：	英文
論文頁數：	92
中文關鍵詞：	B介子、稀有衰變、分支比、CP破壞、Belle偵測器、B介子工廠
外文關鍵詞：	B meson, rare decay, branching ratios, CP violation, Belle detector, B-factory
相關次數：	點閱：2 下載：0
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我們使用B介子工廠在Upsilon介子的4s態共振質量下所累積的10.5/fb資料，
研究了兩個稀有衰變(B^0 -> Rho Pi及B^0 -> Rho K)的衰變分支比。

其中B^0 -> Rho Pi的衰變分支比為20.2+8.3-6.6x10^-6。

而由於B^0 -> Rho K的資料仍不足，結果尚不明顯，我們基於90%的信心水準，

提供了的衰變分支比上限為23.6x10^-6。

With integrated luminosity 10.5 fb^-1 data acquired at Belle,
we have studied two charmless hadronic B decay modes,

B^0 -> rho pi and B^0 -> rho K.

In this study, we have measured the branching fraction of

B^0 -> rho pi to be 20.2+8.3-6.6 x 10^-6 and

because the significance of the B^0 -> rho K channel is still

small, we only give the upper limit of this mode to be

< 23.6 x 10^-6 at 90% confidence level.

{0.1}Abstract}{2}
{1}Introduction}{1}

{1.1}Motivation}{1}

{1.2}The CP violation}{2}

{1.3}The CKM matrix}{2}

{1.4}The Measurements of the Unitary Triangle}{3}

{2}KEK B-Factory}{5}

{2.1}KEKB}{5}

{2.2}Belle Detector}{7}

  {2.2.1}Beam Pipe}{7}

  {2.2.2}EFC}{9}

  {2.2.3}SVD}{9}

  {2.2.4}CDC}{10}

  {2.2.5}ACC}{10}

  {2.2.6}TOF}{10}

  {2.2.7}ECL}{10}

  {2.2.8}KLM}{11}

{3}Data Sample and Event Selection}{21}

{3.1}Data sample}{21}

{3.2}Event selection}{22}

  {3.2.1}Particle selection}{23}

  {3.2.2}Gamma selection}{23}

  {3.2.3}$\pi ^0$ reconstruction}{23}

  {3.2.4}$K/\pi $ separation}{23}

  {3.2.5}$\rho $ reconstruction}{25}

{3.3}B candidates selection}{25}

  {3.3.1}Beam constrained mass}{25}

  {3.3.2}Energy difference($\Delta E$)}{27}

{3.4}B\=B Background}{28}

{3.5}Continuum Background}{28}

{4}Event Shape Variables}{31}

{4.1}Event shape variables}{31}

  {4.1.1}Thrust Angle $\mathop {\mathgroup \symoperators cos}\nolimits \theta _T$}{31}

  {4.1.2}Spherocity $S_\perp $}{33}

  {4.1.3}Fox-Wolfram momenta}{34}

  {4.1.4}B Meson Flight Direction $\mathop {\mathgroup \symoperators cos}\nolimits \theta ^{*}_{B}$}{34}

  {4.1.5}Helicity angle $\mathop {\mathgroup \symoperators cos}\nolimits \theta _H$}{34}

{4.2}Modified Fox-Wolfram Variable}{36}

{5}Methodology and Fitting Results}{39}

{5.1}Analysis Approaches}{39}

  {5.1.1}Slice Cut Method}{39}

  {5.1.2}Fisher's discriminant}{40}

{5.2}Likelihood Ratio Cut}{43}

{5.3}Fit results}{45}

  {5.3.1}$M_b$ and $\Delta E$ shapes}{45}

  {5.3.2}Signal Yields}{48}

{6}BR Measurements and Conclusion}{57}

{6.1}Reconstruction Efficiency}{57}

  {6.1.1}Tracking Efficiency}{57}

  {6.1.2}$\pi ^0$ Efficiency}{60}

{6.2}Systematics Error Study}{60}

  {6.2.1}Systematics on Particle Identification}{60}

  {6.2.2}Fitting Systematics}{61}

{6.3}Breaching Ratio Measurements}{62}

{6.4}Conclusions and Prospections}{63}

{A}appendix}{73}

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