Search for $B^{+}\to D^{*+}{\pi }^0$ Decay

We report on a search for the doubly Cabibbo suppressed decay $B^{+}\to D^{*+}{\pi }^0$, based on a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find no significant signal and set an upper limit of $\mathcal{B}(B^{+}\to D^{*+}{\pi }^0)<3.6\times {10}^{-6}$ at the 90% confidence level. This limit can be used to constrain the ratio between suppressed and favored $B\to D^{*}\pi$ decay amplitudes, $r<0.051$, at the 90% confidence level.

Figure 1

Feynman tree diagrams for (a) CFD $B^0\to D^{*-}{\pi }^{+}$ with the CKM coupling $V_{cb}^{*}{V}_{ud}$, and (b) DCSD $B^{+(0)}\to D^{*+}{\pi }^{0(-)}$ with the coupling $V_{ub}^{*}{V}_{cd}$.

Figure 2

Projections of the unbinned two-dimensional likelihood fit to data in the region $|\Delta E|<0.25\mathrm{GeV}$ and $5.20\mathrm{GeV}/c^2<M_{\mathrm{bc}}<5.29\mathrm{GeV}/c^2$. (a) $\Delta E$ distribution for $5.27\mathrm{GeV}/c^2<M_{\mathrm{bc}}<5.29\mathrm{GeV}/c^2$ with a magnified view of $|\Delta E|<0.07\mathrm{GeV}$ in the inset. (b) $M_{\mathrm{bc}}$ distribution for $|\Delta E|<0.1\mathrm{GeV}$. The points with error bars represent the data, while the curves represent the various components from the fit: signal (thick solid line), continuum (dash-dotted line), ${\overline{B}}^0\to D^{*+}{\rho }^{-}$ decay (dotted line), other $B$ decays (dashed line), and the sum of all components (thin solid line).