标题： $D^0\rightarrow \bar{K}^0π^-e^+ν_e$的半轻子衰变研究 显示英文标题

标题： Study of the semileptonic decay $D^0\rightarrow \bar{K}^0π^-e^+ν_e$

摘要： 我们报告了对半轻子衰变$D^0 \rightarrow \bar{K}^0\pi^-e^+\nu_{e}$的改进研究，该研究基于在 BEPCII 对撞机上以 3.773~GeV 的质心系能量收集的$7.9~\mathrm{fb}^{-1}$的$e^+e^-$粒子湮灭数据，使用 BESIII 探测器。 该衰变的分支比被测量为$\mathcal{B}(D^0\rightarrow \bar{K}^0\pi^-e^+\nu_{e}) = (1.444 \pm 0.022_{\rm stat} \pm 0.024_{\rm syst})\%$，这是目前最精确的测量结果，其中第一个不确定度是统计性的，第二个是系统性的。 基于对该衰变动力学的研究，我们发现该衰变主要由$K^{*}(892)^-$成分主导，并给出了其分支比的改进测量值为$\mathcal{B}(D^0\rightarrow K^{*}(892)^-e^+\nu_e) = (2.039 \pm 0.032_{\rm stat} \pm 0.034_{\rm syst})\%$。 我们还确定了介子形式因子的比值在$K^{*}(892)^-e^+\nu_e$衰变中为$r_{V} = V(0)/A_1(0) = 1.48 \pm 0.05_{\rm stat} \pm 0.02_{\rm syst}$和$r_{2} = A_2(0)/A_1(0) = 0.70 \pm 0.04_{\rm stat} \pm 0.02_{\rm syst}$，其中$V(0)$是矢量形式因子，$A_{1,2}(0)$是轴矢形式因子。 此外，$\bar{K}^0\pi^-$ $\mathcal{S}$波分量被发现占总衰变率的$(5.87 \pm 0.32_{\rm stat} \pm 0.16_{\rm syst})\%$，对应于分支比为$\mathcal{B}[D^0\rightarrow (\bar{K}^0\pi^-)_{S-{\rm wave}}e^+\nu_e] = (0.085 \pm 0.005_{\rm stat} \pm 0.003_{\rm syst})\%$。 显示英文摘要

摘要： We report an improved study of the semileptonic decay $D^0 \rightarrow \bar{K}^0\pi^-e^+\nu_{e}$ based on a sample of $7.9~\mathrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected at a center-of-mass energy of 3.773~GeV with the BESIII detector at the BEPCII collider. The branching fraction of this decay is measured to be $\mathcal{B}(D^0\rightarrow \bar{K}^0\pi^-e^+\nu_{e}) = (1.444 \pm 0.022_{\rm stat} \pm 0.024_{\rm syst})\%$, which is the most precise to date, where the first uncertainty is statistical and the second is systematic. Based on investigation of the decay dynamics, we find that the decay is dominated by the $K^{*}(892)^-$ component and present an improved measurement of its branching fraction to be $\mathcal{B}(D^0\rightarrow K^{*}(892)^-e^+\nu_e) = (2.039 \pm 0.032_{\rm stat} \pm 0.034_{\rm syst})\%$. We also determine the ratios of the hadronic form factors for the $K^{*}(892)^-e^+\nu_e$ decay to be $r_{V} = V(0)/A_1(0) = 1.48 \pm 0.05_{\rm stat} \pm 0.02_{\rm syst}$ and $r_{2} = A_2(0)/A_1(0) = 0.70 \pm 0.04_{\rm stat} \pm 0.02_{\rm syst}$, where $V(0)$ is the vector form factor and $A_{1,2}(0)$ are the axial form factors. In addition, the $\bar{K}^0\pi^-$ $\mathcal{S}$-wave component is found to account for $(5.87 \pm 0.32_{\rm stat} \pm 0.16_{\rm syst})\%$ of the total decay rate, corresponding to a branching fraction of $\mathcal{B}[D^0\rightarrow (\bar{K}^0\pi^-)_{S-{\rm wave}}e^+\nu_e] = (0.085 \pm 0.005_{\rm stat} \pm 0.003_{\rm syst})\%$.