Precision measurement of the natural line width of the $D^{*+}$ at {\sc BaBar}

We measure the total width of the $D^*(2010)^+$ in the transition $D^{*+}\rightarrow D^0 \pi^+$, where the $D^0$ is reconstructed in the decay modes $D^0 \rightarrow K^-\pi^+$, $D^0 \rightarrow K^-\pi^+\pi^0$, $D^0 \rightarrow K_{S}^{0}\pi^-\pi^+$, and $D^0 \rightarrow K^-\pi^+\pi^-\pi^+$. Our data sample corresponds to an integrated luminosity of 487 fb$^{-1}$, more than 50 times greater than for the current best measurment of the $D^{*+}$ width. The data were recorded at center-of-mass energies $10.58$ and $10.54$ GeV with the {\sc BaBar} detector at the PEP II asymmetric energy $e^+e^-$ collider. We use simulated events to model the resolution in $\Delta m$, the difference between the reconstructed invariant masses of the $D^{*+}$ and $D^0$ candidates. We obtain the $D^{*+}$ width by fitting the measured $\Delta m$ distribution to a Breit-Wigner lineshape convolved with the resolution function.