Measurement of the absolute branching fractions $B\to D\pi$, $D^{*}\pi$, $D^{**}\pi$ with a missing mass method

We present branching fraction measurements of charged and neutral $B$ decays to $D{\pi }^{-}$, $D^{*}{\pi }^{-}$, and $“D^{**}”{\pi }^{-}$ with a missing mass method, based on a sample of $231\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ pairs collected by the BABAR detector at the PEP-II $e^{+}{e}^{-}$ collider. One of the $B$ mesons is fully reconstructed and the other one decays to a reconstructed charged $\pi$ and a companion charmed meson identified by its recoil mass, inferred by kinematics. Here “$D^{**}$” refers to the sum of all the nonstrange charm meson states with masses in the range $2.2–2.8\mathrm{GeV}/c^2$. We measure the branching fractions: $\mathcal{B}(B^{-}\to D^0{\pi }^{-})=(4.49\pm 0.21\pm 0.23)\times {10}^{-3}$, $\mathcal{B}(B^{-}\to D^{*0}{\pi }^{-})=(5.13\pm 0.22\pm 0.28)\times {10}^{-3}$, $\mathcal{B}(B^{-}\to “D^{**0}”{\pi }^{-})=(5.50\pm 0.52\pm 1.04)\times {10}^{-3}$, $\mathcal{B}({\overline{B}}^0\to D^{+}{\pi }^{-})=(3.03\pm 0.23\pm 0.23)\times {10}^{-3}$, $\mathcal{B}({\overline{B}}^0\to D^{*+}{\pi }^{-})=(2.99\pm 0.23\pm 0.24)\times {10}^{-3}$, $\mathcal{B}({\overline{B}}^0\to “D^{**+}”{\pi }^{-})=(2.34\pm 0.65\pm 0.88)\times {10}^{-3}$, and their ratios.

Figure 1

$m_{\mathrm{ES}}$ spectra of reconstructed (a) $B^{+}$ and (b) $B^0$ candidates. The solid curve is the sum of the fitted signal and background whereas the dashed curve is the background component only.

Figure 2

Top: missing mass distributions obtained in the recoil of $B^{+}$ (a) and $B^0$ (b). The points with error bars show the data and the histograms show the background contributions ($b\overline{b}$ and $q\overline{q}$ $(q=c,u,d,s)$) predicted by the MC simulation. Bottom: background-subtracted missing mass spectra for $B^{+}$ (c) and $B^0$ (d). The curves show the result of the fits to the $D\pi$ and $D^{*}\pi$ components.