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$B^0 \to K^0π^0$衰变中CP不对称性的测量

Measurement of CP asymmetries in $B^0 \to K^0π^0$ decays

M. Fujikawa, Y. Yusa

备注：
6 pages, 3 figures
发表信息：
Phys.Rev.D81:011101,2010
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摘要：

我们报告测量CP破坏参数$B^0 \to K^0 π^0$衰变的基础上收集的数据样本的$657 \times 10^6 B\bar{B}$对与贝尔探测器在KEKB $e^+ e^-$不对称能量对撞机。我们使用$B^0 \to K^0_S π^0$衰变的混合诱导和直接$CP$违反不对称测量和$B^0 \to K^0_L π^0$衰变的直接CP违反测量。得到的CP破坏参数是$\sin 2 ϕ_1^{\rm eff} = +0.67 \pm 0.31{(stat)} \pm 0.08 {(syst)}$和$\mathcal{A}_{K^0 π^0} = +0.14 \pm 0.13{(stat)} \pm 0.06 {(syst)}$。测量$B^0 \to K^0 π^0$衰变的分支分数为$\mathcal{B}(B^0 \to K^0 π^0) = (8.7\pm0.5 (\rm{stat.})\pm0.6 (\rm{syst.}))\times 10^{-6}$。观测到的$\mathcal{A}_{K^0 π^0}$值与根据同位旋求和规则预期的值相差1.9个标准差。

英文摘要：

We report measurements of CP violation parameters in $B^0 \to K^0 π^0$ decays based on a data sample of $657 \times 10^6 B\bar{B}$ pairs collected with the Belle detector at the KEKB $e^+ e^-$ asymmetric-energy collider. We use $B^0 \to K^0_S π^0$ decays for both mixing-induced and direct $CP$ violating asymmetry measurements and $B^0 \to K^0_L π^0$ decays for the direct CP violation measurement. The CP violation parameters obtained are $\sin 2 ϕ_1^{\rm eff} = +0.67 \pm 0.31{(stat)} \pm 0.08 {(syst)}$ and $\mathcal{A}_{K^0 π^0} = +0.14 \pm 0.13{(stat)} \pm 0.06 {(syst)}$. The branching fraction of $B^0 \to K^0 π^0$ decay is measured to be $\mathcal{B}(B^0 \to K^0 π^0) = (8.7\pm0.5 (\rm{stat.})\pm0.6 (\rm{syst.}))\times 10^{-6}$. The observed $\mathcal{A}_{K^0 π^0}$ value differs by 1.9 standard deviations from the value expected from an isospin sum rule.

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