Study of inclusive $B^{-}$ and ${\overline{B}}^0$ decays to flavor-tagged $D$, $D_s$, and ${\mathit{\Lambda }}_c^{+}$

We report on a study of inclusive $B^{-}$ and ${\overline{B}}^0$ meson decays to $D^{0}X$, ${\overline{D}}^{0}X$, $D^{+}X$, $D^{-}X$, $D_s^{+}X$, $D_s^{-}X$, ${\mathit{\Lambda }}_c^{+}X$, ${\overline{\mathit{\Lambda }}}_c^{-}X$, based on a sample of $231\times {10}^6$ $B\overline{B}$ events recorded with the BABAR detector at the $\mathit{{\rm Y}}(4S)$ resonance. Events are selected by completely reconstructing one $B$ and searching for a reconstructed charm particle in the rest of the event. From the measured branching fractions of these decays, we infer the number of charm and anticharm particles per $\overline{B}$ decay, separately for charged and neutral parents. We derive the total charm yield per $B^{-}$ decay, $n_c^{-}=1.208\pm 0.023\pm {0.040}_{-0.029}^{+0.035}$, and per ${\overline{B}}^0$ decay, $n_c^0=1.203\pm 0.030\pm {0.034}_{-0.035}^{+0.044}$ where the first uncertainty is statistical, the second is systematic, and the third reflects the charm branching-fraction uncertainties. We also present the charm momentum distributions measured in the $\overline{B}$ rest frame.

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

Charm (left) and anticharm (right) mass spectra in the recoil of $B^{+}$ candidates, for the subsample of events with $m_{\mathrm{ES}}>5.270\mathrm{GeV}/c^2$ ($B$ signal region). The solid curve shows the result of the two-dimensional fit. The dark shaded areas show the contribution of reconstructed $D$, $\overline{D}$, ${\mathit{\Lambda }}_c^{+}$ and ${\overline{\mathit{\Lambda }}}_c^{-}$ signal in the recoil of combinatorial $B_{{\mathrm{rec}}^{\prime }\mathrm{d}}^{+}$ background. The light shaded area corresponds to the fitted combinatorial (anti-) charm background.

Figure 3

Charm (left) and anticharm (right) mass spectra as for Fig. 2, but in the recoil of ${\overline{B}}^0$ candidates.

Figure 4

$D_s^{+}$ (left) and $D_s^{-}$ (right) mass spectra in the recoil of $B^{+}$ candidates, for the subsample of events with $m_{\mathrm{ES}}>5.270\mathrm{GeV}/c^2$ ($B$ signal region). The solid curve shows the result of the two-dimensional fit. The dark shaded areas show the contribution of reconstructed $D_s^{+}$, $D_s^{-}$ signal in the recoil of combinatorial $B_{{\mathrm{rec}}^{\prime }\mathrm{d}}^{+}$ background. The light shaded area corresponds to the fitted combinatorial (anti-) charm background. The Gaussian peak at the $D^{+}$ mass accounts for reconstructed $D^{+}$ signal [26].

Figure 5

$D_s^{+}$ and $D_s^{-}$ mass spectra as for Fig. 4, but in the recoil of ${\overline{B}}^0$ candidates.

Figure 6

Momentum spectra, in the $B^{-}$ rest frame, of correlated (left) and anticorrelated (right) charm particles : $D^0/{\overline{D}}^0$ (a), (b), $D^{\pm }$ (c)(d), $D_s^{\pm }$ (e), (f), ${\mathit{\Lambda }}_c^{\pm }$ (g), (h). The error bars are statistical only. The histogram in frame (f) represents the contribution of $B^{-}\to D^{(*)0}{D}_s^{(*)-}$ two-body decays assuming the branching fractions of Ref. 2, 24.

Figure 7

Momentum spectra, in the ${\overline{B}}^0$ rest frame, of correlated (left) and anticorrelated (right) charm particles : $D^0/{\overline{D}}^0$ (a), (b), $D^{\pm }$ (c)(d), $D_s^{\pm }$ (e), (f), ${\mathit{\Lambda }}_c^{\pm }$ (g), (h). The error bars are statistical only.