We report a study of the decay $D^0\to {\overline{K}}^0{\pi }^{-}{e}^{+}{\nu }_e$ based on a sample of $2.93{\mathrm{fb}}^{-1}$ $e^{+}{e}^{-}$ annihilation data collected at the center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII collider. The total branching fraction is determined to be $\mathcal{B}(D^0\to {\overline{K}}^0{\pi }^{-}{e}^{+}{\nu }_e)=(1.434\pm 0.029(\mathrm{stat}.)\pm 0.032(\mathrm{syst}.))\%$, which is the most precise to date. According to a detailed analysis of the involved dynamics, we find this decay is dominated with the $K^{*}(892{)}^{-}$ contribution and present an improved measurement of its branching fraction to be $\mathcal{B}(D^0\to K^{*}(892{)}^{-}{e}^{+}{\nu }_e)=(2.033\pm 0.046(\mathrm{stat}.)\pm 0.047(\mathrm{syst}.))\%$. We further access their hadronic form-factor ratios for the first time as $r_V=V(0)/A_1(0)=1.46\pm 0.07(\mathrm{stat}.)\pm 0.02(\mathrm{syst}.)$ and $r_2=A_2(0)/A_1(0)=0.67\pm 0.06(\mathrm{stat}.)\pm 0.01(\mathrm{syst}.)$. In addition, we observe a significant ${\overline{K}}^0{\pi }^{-}S$-wave component accounting for $(5.51\pm 0.97(\mathrm{stat}.)\pm 0.62(\mathrm{syst}.))\%$ of the total decay rate.

• Received 28 November 2018

DOI:https://doi.org/10.1103/PhysRevD.99.011103

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Published by the American Physical Society