Precision measurement of the $D^{*0}$ decay branching fractions

Using $482{\mathrm{pb}}^{-1}$ of data taken at $\sqrt{s}=4.009\mathrm{GeV}$, we measure the branching fractions of the decays of $D^{*0}$ into $D^0{\pi }^0$ and $D^0\gamma$ to be $\mathcal{B}(D^{*0}\to D^0{\pi }^0)=(65.5\pm 0.8\pm 0.5)\%$ and $\mathcal{B}(D^{*0}\to D^0\gamma )=(34.5\pm 0.8\pm 0.5)\%$, respectively, by assuming that the $D^{*0}$ decays only into these two modes. The ratio of the two branching fractions is $\mathcal{B}(D^{*0}\to D^0{\pi }^0)/\mathcal{B}(D^{*0}\to D^0\gamma )=1.90\pm 0.07\pm 0.05$, which is independent of the assumption made above. The first uncertainties are statistical and the second ones systematic. The precision is improved by a factor of 3 compared to the present world average values.

Figure 1

Comparisons between data and MC simulation, summing the five modes listed in Table 1: (a) the ${\chi }^2$ distribution, (b) the momentum of $D^0$, (c) the momentum of ${\overline{D}}^0$, and (d) the square of the $D^0{\overline{D}}^0$ recoil mass. Dots with error bars are data, the open red histograms are MC simulations, and the filled green histograms are background events from the inclusive MC sample. The signal MCs are normalized to data according to the number of events, and background events from the inclusive MC sample are normalized to data by luminosity.

Figure 2

The branching fraction of $D^{*0}\to D^0{\pi }^0$. The dots with error bars are the results from the five modes; the band represents the weighted average. Only statistical uncertainties are included.

Figure 3

Comparison of the branching fraction of $D^{*0}\to D^0{\pi }^0$ from this work and from previous experiments. Dots with error bars are results from different experiments, and the band is the result from this work with both statistical and systematic uncertainties.