Phys. Rev. D 78, 112003 (2008) - Measurements of $\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\overline{p})$ and $\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\overline{p}{\ensuremath{\pi}}^{\ensuremath{-}})$ and studies of ${\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ resonances

Measurements of $B ({\bar{B}}^{0} \to Λ_{c}^{+} \bar{p})$ and $B (B^{-} \to Λ_{c}^{+} \bar{p} π^{-})$ and studies of $Λ_{c}^{+} π^{-}$ resonances

B. Aubert et al. (BABAR Collaboration)

Phys. Rev. D 78, 112003 – Published 29 December 2008

Abstract

We present an investigation of the decays ${\bar{B}}^{0} \to Λ_{c}^{+} \bar{p}$ and $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$ based on $383 \times 10^{6}$ $Υ (4 S) \to B \bar{B}$ decays recorded with the BABAR detector. We measure the branching fractions of these decays; their ratio is $B (B^{-} \to Λ_{c}^{+} \bar{p} π^{-}) / B ({\bar{B}}^{0} \to Λ_{c}^{+} \bar{p}) = 15.4 \pm 1.8 \pm 0.3$ . The $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$ process exhibits an enhancement at the $Λ_{c}^{+} \bar{p}$ threshold and is a laboratory for searches for excited charm baryon states. We observe the resonant decays $B^{-} \to Σ_{c} (2455)^{0} \bar{p}$ and $B^{-} \to Σ_{c} (2800)^{0} \bar{p}$ but see no evidence for $B^{-} \to Σ_{c} (2520)^{0} \bar{p}$ . This is the first observation of the decay $B^{-} \to Σ_{c} (2800)^{0} \bar{p}$ ; however, the mass of the observed excited $Σ_{c}^{0}$ state is $(2846 \pm 8 \pm 10) MeV / c^{2}$ , which is somewhat inconsistent with previous measurements. Finally, we examine the angular distribution of the $B^{-} \to Σ_{c} (2455)^{0} \bar{p}$ decays and measure the spin of the $Σ_{c} (2455)^{0}$ baryon to be $1 / 2$ , as predicted by the quark model.