Precise Measurement of the Form Factors in $ {D}^{0}\to {K}^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$, and Test of Lepton Universality with $ {D}^{0}\to {K}^{*}(892{)}^{-}{\ell }^{+}{\nu }_{\ell }$ Decays

We report a study of the semileptonic decay $ {D}^{0}\to {\overline{K}}^{0}{\pi }^{-}{\mu }^{+}{\nu }_{\mu }$ based on a sample of $ 7.9\text{}\text{}{\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 the decay is measured for the first time to be $ \mathcal{B}({D}^{0}\to {\overline{K}}^{0}{\pi }^{-}{\mu }^{+}{\nu }_{\mu })=(1.373\pm 0.02{0}_{\mathrm{stat}}\pm 0.02{3}_{\mathrm{syst}})\%$, where the first uncertainty is statistical and the second is systematic. Based on the investigation of the decay dynamics, we find that the decay is dominated by the $ {K}^{*}(892{)}^{-}$ resonance with the branching fraction measured to be $ \mathcal{B}({D}^{0}\to {K}^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu })=(1.948\pm 0.03{3}_{\mathrm{stat}}\pm 0.03{6}_{\mathrm{syst}})\%$. We also determine the hadronic form factors for the $ {D}^{0}\to {K}^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay to be $ {r}_{V}=V(0)/{A}_{1}(0)=1.46\pm 0.1{1}_{\mathrm{stat}}\pm 0.0{4}_{\mathrm{syst}}$, $ {r}_{2}={A}_{2}(0)/{A}_{1}(0)=0.71\pm 0.0{8}_{\mathrm{stat}}\pm 0.0{3}_{\mathrm{syst}}$, and $ {A}_{1}(0)=0.609\pm 0.00{8}_{\mathrm{stat}}\pm 0.00{8}_{\mathrm{syst}}$, where $ V(0)$ is the vector form factor and $ {A}_{1,2}(0)$ are the axial-vector form factors evaluated at $ {q}^{2}=0$. The $ {A}_{1}(0)$ is measured for the first time in $ {D}^{0}\to {K}^{*}(892{)}^{-}{\mu }^{+}{\nu }_{\mu }$ decay. Averaging the form factor parameters that we reported previously in $ {D}^{0}\to {K}^{*}(892{)}^{-}(\to {\overline{K}}^{0}{\pi }^{-}){e}^{+}{\nu }_{e}$ and $ {D}^{0}\to {K}^{*}(892{)}^{-}(\to {K}^{-}{\pi }^{0}){\mu }^{+}{\nu }_{\mu }$ decays, we obtain $ {r}_{V}=1.456\pm 0.04{0}_{\mathrm{stat}}\pm 0.01{6}_{\mathrm{syst}}$, $ {r}_{2}=0.715\pm 0.03{1}_{\mathrm{stat}}\pm 0.01{4}_{\mathrm{stat}}$, and $ {A}_{1}(0)=\phantom{\rule{0ex}{0ex}}0.614\pm 0.00{5}_{\mathrm{stat}}\pm 0.00{4}_{\mathrm{syst}}$. This is the most precise determination of the form factor parameters to date measured in $ D\to {K}^{*}(892)$ transitions, which provide the most stringent test on various theoretical models.