Measurement of the $D^{+}\to {\pi }^{+}{\pi }^0$ and $D^{+}\to K^{+}{\pi }^0$ branching fractions

We present measurements of the branching fractions for the Cabbibo suppressed decays $D^{+}\to {\pi }^{+}{\pi }^0$ and $D^{+}\to K^{+}{\pi }^0$ based on a data sample corresponding to an integrated luminosity of $124.3{\mathrm{fb}}^{-1}$. The data were taken with the BABAR detector at the PEP-II $B$ Factory operating on and near the $\mathit{{\rm Y}}(4S)$ resonance. We find $\mathcal{B}(D^{+}\to {\pi }^{+}{\pi }^0)=(1.25\pm 0.10\pm 0.09\pm 0.04)\times {10}^{-3}$ and $\mathcal{B}(D^{+}\to K^{+}{\pi }^0)=(2.52\pm 0.47\pm 0.25\pm 0.08)\times {10}^{-4}$, where the first uncertainty is statistical, the second systematic and the last error is due to the uncertainties in the absolute branching fraction scale for $D^{+}$ mesons. This represents the first observation of the doubly Cabibbo-suppressed $D^{+}\to K^{+}{\pi }^0$ decay mode and a new measurement of the $D^{+}\to {\pi }^{+}{\pi }^0$ branching fraction.

Figure 1

$\Delta m$ distribution for simulated $D^{*+}\to D^{+}{\pi }^0$, $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ events. The vertical lines mark the signal and sideband regions defined in the text. The solid line shows the result of the fit; the background is given by the dash-dotted line.

Figure 2

${\pi }^{+}{\pi }^0$ invariant mass distribution in the $D^{+}\to {\pi }^{+}{\pi }^0$ signal mode for simulated data. The background is modeled by a first order polynomial (dash-dotted) and an exponential (dotted), while the signal is fitted by a bifurcated Gaussian function. The dashed line shows the peaking $D^{+}$ background determined from the $\Delta m$ sideband fit.

Figure 3

Likelihood fit results for the full data sample for (a) $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$, (b) $D^{+}\to {\pi }^{+}{\pi }^0$, and (c) $D^{+}\to K^{+}{\pi }^0$ decays. The dashed lines show the projected backgrounds in the signal region.