论文标题
通过Kloe实验的$ k_s \至πeν$分支的测量
Measurement of the $K_S \to πe ν$ branching fraction with the KLOE experiment
论文作者
论文摘要
衰减的分支$ k_s \至πeν$的分支分数是用$ ϕ \ to k_l k_l k_s $衰减的3亿美元$ k_s $梅森的样本测量的。信号衰减是由具有运动变量和飞行时间测量的增强决策树选择的。 $ k_l \toπeν$衰减的数据控制样本用于评估信号选择效率。适合重建的电子质量分布发现49647 $ \ pm $ 316信号事件。归一化为$ k_s \至π^+π^ - $衰减事件的分支分数的结果为$ \ Mathcal {b}（k_s \toπeVtoπeV）=（7.211 \ pm 0.046 _ {\ rm Stat}}与我们先前的测量相结合给出了$ \ mathcal {b}（k_s \toπeν）=（7.153 \ pm 0.037 _ {\ rm stat} \ pm 0.043 _ {\ rm syst}）\ times10^{ - 4} $。从这个值我们得出$ f _+（0）| v_ {us} | = 0.2170 \ pm 0.009 $。
The branching fraction for the decay $K_S \to πe ν$ has been measured with a sample of 300 million $K_S$ mesons produced in $ϕ\to K_L K_S$ decays recorded by the KLOE experiment at the DA$Φ$NE $e^+e^-$ collider. Signal decays are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of $K_L \to πe ν$ decays are used to evaluate signal selection efficiencies. A fit to the reconstructed electron mass distribution finds 49647$\pm$316 signal events. Normalising to the $K_S \to π^+π^-$ decay events the result for the branching fraction is $\mathcal{B}(K_S \to πe ν) = (7.211 \pm 0.046_{\rm stat} \pm 0.052_{\rm syst}) \times10^{-4}$. The combination with our previous measurement gives $\mathcal{B}(K_S \to πe ν) = (7.153 \pm 0.037_{\rm stat} \pm 0.043_{\rm syst}) \times10^{-4}$. From this value we derive $f_+(0)|V_{us}| = 0.2170 \pm 0.009$.
