Measurement of the mass of the $D^0$ meson

We report a measurement of the $D^0$ meson mass using the decay chain $D^{*}(2010{)}^{+}\to D^0{\pi }^{+}$ with $D^0\to K^{-}{K}^{-}{K}^{+}{\pi }^{+}$. The data were recorded with the BABAR detector at center-of-mass energies at and near the $\mathit{{\rm Y}}(4S)$ resonance, and correspond to an integrated luminosity of approximately $477{\mathrm{fb}}^{-1}$. We obtain $m(D^0)=(1864.841\pm 0.048\pm 0.063)\mathrm{MeV}$, where the quoted errors are statistical and systematic, respectively. The uncertainty of this measurement is half that of the best previous measurement.

Figure 1

Results of the extended, unbinned maximum likelihood fit to the reconstructed $D^0$ mass distribution. Normalized residuals are defined as $(N_o-N_p)/\sqrt{N_p}$, where $N_o$ and $N_p$ are observed and predicted numbers of events, respectively.

Figure 2

The value of $m(D^0)$ obtained from fits to data divided into disjoint subsets in (a) $\varphi$, (b) $p_{\mathrm{lab}}(D^0)$, and (c) $\Delta m$. Each point represents an individual fit, and the horizontal line indicates the nominal fit result; the points are plotted at the mean value in the range, and the uncertainty in the mean values is smaller than the marker size.