The Properties of Semileptonic Decays of Charmed D Mesons.

The MARK III collaboration has collected a large sample of D mesons produced at the Ψ(3770) resonance. The reconstruction of several thousand hadronic D decays makes possible for the first time the reconstruction of exclusive semileptonic D decays. Absolute branching ratios are measured for the nine decays D0 → K- e+ νe, D0 → K- π0 e+ νe, D0 → K0 π- e+ νe, D+ → K0 e+ νe, D+ → K- π+ e+ νe, D0 → π- e+ νe, D0 → K- μ+ νμ, D0 → K0 π- μ+ νμ, and D+ → K0 μ+ νμ. The sums of the exclusive branching ratios are in good agreement with the inclusive semileptonic branching ratios measured by the MARK III. The rate of the Cabibbo-suppressed decays is consistent with the predicted rate. The contribution of the K*(892) to the K-π invariant mass spectrum for decays of the type D → K π e+ νe is found to be about 55%. The vector form factor in the decays D0 → K- e+ νe and D0 → K- μ+ νμ is measured and found to be consistent with a simple pole form.