标题： 新物理在$c\to (s,d)\ell^+ν_\ell$转换中的影响研究 显示英文标题

标题： Investigation of Effects of New Physics in $c\to (s,d)\ell^+ν_\ell$ Transitions

摘要： 最近由$b\to c \ell^- \bar\nu_\ell$转换引发的衰变中的异常现象引发了关于在由$c\to (s,d)\ell^+\nu_\ell$转换引发的$D$衰变中此类现象的问题。 在实验方面，当前对纯轻子和半轻子$D$衰变的测量结果与标准模型预测一致，这种一致性可以用来限制新物理（NP）贡献。 在本工作中，我们通过假设描述包括全部四费米子算符集的$c\to (s,d)\ell^+\nu_\ell$转换的一般有效哈密顿量来扩展标准模型。 在最新的实验数据范围内，我们对每个算符对应的威尔逊系数进行了最小$\chi^2$拟合。 结果表明，缪子区间的标量算符的威尔逊系数在${\cal O}(10^{-2})$的数量级，其他则在${\cal O}(10^{-3})$的数量级。 轻子味普遍性可能被标量算符破坏。 我们还利用标量和张量算符拟合后的威尔逊系数计算了分支比、最终矢量介子和轻子的正向-反向不对称性以及极化。 发现纯轻子衰变对标量算符非常敏感。 NP 对带有电子的半轻子衰变的影响可以忽略不计，而对于带有缪子的半轻子衰变，标量算符的影响会在缪子的正向-反向不对称性和极化中显现出来，即$D \to P\mu^+ \nu_\mu$。 BESIII 和 Belle II 实验的未来测量将有助于我们检验 NP 的影响，并进一步检验新物理模型。 显示英文摘要

摘要： Recent anomalies in decays induced by $b\to c \ell^- \bar\nu_\ell$ transitions raise the question about such phenomena in the $D$ decays induced by $c\to (s,d)\ell^+\nu_\ell$ transitions. In the experimental side, current measurements on the pure leptonic and semileptonic $D$ decays agree with the standard model predictions, such agreements can be used to constrain the new physics (NP) contributions. In this work, we extend the standard model by assuming general effective Hamiltonians describing the $c\to (s,d)\ell^+\nu_\ell$ transitions including the full set of the four-fermion operators. Within the latest experimental data, we perform a minimum $\chi^2$ fit of the Wilson coefficient corresponding to each operator. The results show that the Wilson coefficients of scalar operators in muon sector are at the order of ${\cal O}(10^{-2})$, and others are at the order of ${\cal O}(10^{-3})$. The lepton flavor universality could be violated by the scalar operators. We also calculate the branching fractions, the forward-backward asymmetries and polarizations of final vector mesons and leptons with the fitted Wilson coefficients of scalar and tensor operators. It is found that the pure leptonic decays are very sensitive to the scalar operators. The effects of NP on the semileptonic decays with electron are negligible, while for the semileptonic decays with muon the effects of scalar operators will show up in the forward-backward asymmetries and polarizations of muon of $D \to P\mu^+ \nu_\mu$. The future measurements in BESIII and Belle II experiments will help us to test effects of NP and to further test new physics models.