$D^{0(+)}\to π^{-(0)}\ell^+ν_\ell$衰变动力学的精确测量
Precision Measurement of Decay Dynamics in $D^{0(+)}\to π^{-(0)}\ell^+ν_\ell$
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中文总结 AI 辅助
该研究利用BESIII探测器数据精确测量特定衰变分支比，研究μ子与正电子通道衰变宽度比率，未发现轻子味普适性违反，通过拟合测量相关物理量乘积及标量电流贡献，结果精度大幅提升。
中文摘要 AI 辅助
利用BESIII探测器在质心能量为3.773 GeV时收集的20.3 fb$^{-1}$的$e^+e^-$碰撞数据，精确测量了$D^0\to \pi^-e^+\nu_e$、$D^0\to \pi^-\mu^+\nu_\mu$、$D^+\to \pi^0e^+\nu_e$和$D^+\to \pi^0\mu^+\nu_\mu$的分支比。全面研究了μ子和正电子通道之间衰变宽度的比率。未发现轻子味普适性违反。通过对这四个衰变的精确测量部分衰变率和首次测量的前后不对称性进行同时拟合，以前所未有的精度测量了强子跃迁形状因子$f^{D\to\pi}_+(0)$与$c\to d$夸克混合元素$|V_{cd}|$的乘积等，各结果精度比之前最佳测量提高2 - 3倍，还首次测量了标量电流贡献的实部和虚部。
英文摘要
The branching fractions of $D^0\to π^-e^+ν_e$, $D^0\to π^-μ^+ν_μ$, $D^+\to π^0e^+ν_e$, and $D^+\to π^0μ^+ν_μ$ are precisely measured, using 20.3 fb$^{-1}$ of $e^+e^-$ collision data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The ratios of the decay widths between muon and positron channels are examined in full, across several four-momentum transfer ranges of $\ell^+ν_{\ell}$. No lepton flavor universality violation is found in the current data. From a simultaneous fit to the precisely measured partial decay rates and the first measured forward-backward asymmetries of these four decays, the product of the hadronic transition form factor, $f^{D\toπ}_+(0)$, and the modulus of the $c\to d$ quark mixing element, $|V_{cd}|$, is measured with unprecedented precision to be $f^{D\toπ}_+(0)|V_{cd}|=0.1425\pm0.0005_{\rm stat.}\pm0.0003_{\rm syst.}$. Taking the value of $|V_{cd}|$ from the standard model global fit and $f^{D\toπ}_+(0)$ derived by the lattice quantum chromodynamics calculation as input, we obtain $f^{D\toπ}_+(0)=0.1425\pm0.0005_{\rm stat.}\pm0.0003_{\rm syst.}$ and $|V_{cd}|=0.2262\pm0.0008_{\rm stat.}\pm0.0005_{\rm syst.}\pm0.0018_{\rm LQCD.}$, respectively. The precision of each result is a factor of 2-3 better than the previous best measurements. Additionally, the real and imaginary parts of the scalar current contribution in the $c\to d \ell^+ν_{\ell}$ transition are measured for the first time to be Re $(C_S^μ)=$ $0.022 \pm 0.023_{\rm stat.}\pm 0.003_{\rm syst.}$ and $|\mathrm{Im} (C_S^μ)|=0.000 \pm 0.038_{\rm stat.}\pm 0.012_{\rm syst.}$.
