Observation of the decay ${\overline{B}}^0\to {\mathit{\Lambda }}_c^{+}\overline{p}{\pi }^0$

In a sample of $467\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II collider at SLAC we have observed the decay ${\overline{B}}^0\to {\mathit{\Lambda }}_c^{+}\overline{p}{\pi }^0$ and measured the branching fraction to be $(1.94\pm 0.17\pm 0.14\pm 0.50)\times {10}^{-4}$, where the uncertainties are statistical, systematic, and the uncertainty on the ${\mathit{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$ branching fraction, respectively. We determine an upper limit of $1.5\times {10}^{-6}$ at 90% C.L. for the product branching fraction $\mathcal{B}({\overline{B}}^0\to {\mathit{\Sigma }}_c^{+}(2455)\overline{p})\times \mathcal{B}({\mathit{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+})$. Furthermore, we observe an enhancement at the threshold of the invariant mass of the baryon-antibaryon pair.

Figure 1

$\Delta E$ distribution for data signal events after all selection cuts (data points) and signal MC events (histogram) normalized to the number of data signal events; signal events are obtained from binwise $m_{\mathrm{ES}}$ fits; dashed lines show the range used for $m_{\mathrm{ES}}$ distributions.

Figure 2

Fitted $m_{\mathrm{ES}}$ distribution without efficiency correction (data points); the result of the fit (solid line) and the background estimate (dashed line) is shown.

Figure 3

Efficiency-corrected $m_{\mathrm{ES}}$ distribution for ${\overline{B}}^0\to {\mathit{\Lambda }}_c^{+}\overline{p}{\pi }^0$ (data points). The result of the fit (solid line) and the background estimate (dashed line) is shown.

Figure 4

Efficiency corrected distribution of the invariant mass $m({\mathit{\Lambda }}_c^{+}\overline{p})$; points are signal data events; histogram shows signal MC events assuming phase space distribution normalized to the number of data events.

Figure 5

Distribution of the invariant mass of the ${\mathit{\Lambda }}_c^{+}{\pi }^0$ system in the region where the ${\mathit{\Sigma }}_c^{+}(2455)$ resonance is expected; points are for data with $m_{\mathrm{ES}}>5.272\mathrm{GeV}/c^2$, the curve shows the fit.