Experimental Study of the Semileptonic DecayD+→K¯*0e+νe

The decay $D^{+}\to K^{-}{\pi }^{+}{e}^{+}{\nu }_e$ has been studied in the Fermilab photoproduction experiment E691. The ratio of branching ratios, $\frac{B(D^{+}\to {\overline{K}}^{*0\mathrm{}}{e}^{+}{\nu }_e)}{B(D^{+}\to K^{-}{\pi }^{+}{\pi }^{+})}$, is found to be 0.49±0.04 ±0.05, corresponding to a $D^{+}\to {\overline{K}}^{*0\mathrm{}}{e}^{+}{\nu }_e$ branching ratio of (4.5±0.7±0.5)%. The branching ratio to the nonresonant ${\left(K^{-}{\pi }^{+}\right)}_{\mathrm{NR}}e{\nu }_e$ final state is found to be less than 0.7% at the 90% confidence level. The ${\overline{K}}^{*0\mathrm{}}$ mesons have a ratio of longitudinal to transverse polarization of 2.4${\pm }_{0.9}^{1.7}$±0.2.