We have observed inclusive production of $D^0$ and $D^{+}$ mesons, and their charge conjugates, in $e^{+}{e}^{-}$ annihilation at 29 GeV on the basis of a data sample of 106 p${\mathrm{b}}^{-1\mathrm{}}$. These signals correspond to $R$ values of $R(D^0+{\bar{D}}^0)=1.8\mathrm{}\pm 0.5$ and $R(D^{+}+D^{-})=1.2\mathrm{}\pm 0.4$. Taking the $D^{+}$ and $D^0$ data together, we measure a charge asymmetry of $A=-0.08\mathrm{}\pm 0.12$ for charmed quarks. A comparison of $R(D+\bar{D})$ with $R(D^{*}+{\bar{D}}^{*})$ obtained via the process $D^{*+}\to D^0{\pi }^{+}$ gives a $\frac{D}{D^{*}}$ ratio of ${1.0}_{-0.2\mathrm{}}^{+0.3\mathrm{}}$, indicating that direct $D^{*}$ production dominates over direct $D$ production.

• Received 25 June 1984

DOI:https://doi.org/10.1103/PhysRevLett.53.1971