Observation of $D^{+}\to K_S^0\ddot{I}{€}^0\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$, Test of Lepton Flavor Universality and First Angular Analysis of $D^{+}\to {\bar{K}}^{\ast }(892{)}^0{\ell }^{+}\hat{I}{½}_{\ell }$

BESIII Collaboration, M. Ablikim, M. N. Achasov +688

We report a study of the semileptonic decays $D^{+}\to K_S^0\ddot{I}{€}^0{\ell }^{+}\hat{I}{½}_{\ell }$ ($\ell =e,\hat{I}¼$) based on $20.3{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected at the center-o…