B^±→h^± h^0之二體稀有衰變與電荷宇稱破壞之量測

Abstract

本篇論文量測帶電B介子衰變至兩個強子機率與電荷宇稱破壞，包括B^+→K^+ π^0, π^+ π^0, K ‾^0 K^+,K^0 π^+和它們的反粒子。以Belle偵測器在正負電子對撞機內收集的772百萬對Ｂ介子做為數據，分析在Υ(4S)共振態的稀有衰變。這個分析是上一次Belle實驗數據量的1.4到1.7倍，實驗的結果也是Belle偵測器以全部的數據做最後一次的更新。 衰變分枝比的實驗結果為： B^+→K^+ π^0=(12.62±0.31(統計)±0.56(系統))×10^(-6) B^+→π^+ π^0=(5.86±0.26±0.38)×10^(-6) B^+→K ‾^0 K^+=(1.11±0.19±0.05)×10^(-6) B^+→K^0 π^+=(23.97±0.53±0.69)×10^(-6) 我們也量測了R_c=1.05±0.03±0.05和R_n=1.04±0.05±0.06，與標準模型在誤差內一致。 電荷宇稱破壞的實驗結果為： B^+→K^+ π^0=+0.043±0.024±0.002 B^+→π^+ π^0=+0.025±0.043±0.007 B^+→K ‾^0 K^+=+0.017±0.168±0.002 B^+→K^0 π^+=-0.014±0.021±0.006 我們確認了電荷宇稱破壞在B^+→K^+ π^0為正值，且在其它衰變中，並無關測到電荷宇稱不對稱。

We report the improved measurements of branching fractions and direct $CP$ violation for charmless $B$ decays to two hardons, $B^pm o h^pm h^0$. $B^+ o K^+ pi^0$, $pi^+ pi^0$, $overline{K}^0 K^+$ and $K^0 pi^+$ decays and their conjugations are studied with the data of 772 million $B overline{B}$ pairs collected at $Upsilon(4S)$ resonance in Belle detector of $e^+e^-$ collider. This data sample is 1.7 times larger than the previous study for branching fraction and $CP$ violation measurements in $B^+ o overline{K}^0 K^+$ and $B^+ K^0 pi^+$ decays. Also, 1.4 times for $CP$ violation measurements in $B^+ o K^+ pi^0$ and $B^+ pi^+ pi^0$. Besides, this study is the final update for Belle detector with all data sample. The branching fraction are measured to be $mathcal{BR}(B^+ o K^+ pi^0)=(12.62pm 0.31pm 0.56) imes 10^{-6}$, $mathcal{BR}(B^+ o pi^+ pi^0)=(5.86pm 0.26pm 0.38) imes 10^{-6}$, $mathcal{BR}(B^+ o overline{K}^0 K^+)=(1.11 ^{+0.19} _{-0.18} pm 0.05) imes 10^{-6}$ and $mathcal{BR}(B^+ o K^0 pi^+)=(23.97 ^{+0.53} _{-0.52} pm 0.69) imes 10^{-6}$. The first error is statistical and the second one is systematic. We also report the rations of partial widths for $B o K pi$ and $pi pi$ decays. $R_c = 1.05pm 0.03pm 0.05$ and $R_n = 1.04pm 0.05pm 0.06$ are consistent with Standard Model expectations.

The direct $CP$ violation measurements are reported to be $mathcal{A}_{cp}(B^+ o K^+ pi^0)=+0.043pm 0.024(stat.)pm 0.002(syst.)$, $mathcal{A}_{cp}(B^+ o pm^+ pi^0)=+0.025pm 0.043pm 0.007$, $mathcal{A}_{cp}(B^+ o overline{K}^0 K^0)=+0.017pm 0.168pm 0.002$ and $mathcal{A}_{cp}(B^+ o K^+ pi^0)=-0.014pm 0.021pm 0.006$. We confirm the positive sign of $mathcal{A}_{cp}$ in $B^+ o K^+ pi^0$ and no charge asymmetry be observed in other decays.