Study of Decay Mechanisms in ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}\overline{p}{\ensuremath{\pi}}^{\ensuremath{-}}$ Decays and Observation of Low-Mass Structure in the ${\ensuremath{\Lambda}}_{c}^{+}\overline{p}$ System

Study of Decay Mechanisms in $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$ Decays and Observation of Low-Mass Structure in the $Λ_{c}^{+} \bar{p}$ System

N. Gabyshev et al. (Belle Collaboration)

Phys. Rev. Lett. 97, 242001 – Published 11 December 2006

Abstract

Using a sample of $152 \times 10^{6}$ $B \bar{B}$ pairs accumulated with the Belle detector at the KEKB $e^{+} e^{-}$ collider, we study the decay mechanism of three-body charmed decay $B^{-} \to Λ_{c}^{+} \bar{p} π^{-}$ . The intermediate two-body decay $B^{-} \to Σ_{c} (2455)^{0} \bar{p}$ is observed for the first time with a branching fraction of $(3.7 \pm 0.7 \pm 0.4 \pm 1.0) \times 10^{- 5}$ and a statistical significance of $8.4 σ$ . We also observe a low-mass enhancement in the $(Λ_{c}^{+} \bar{p})$ system, which can be parametrized as a Breit-Wigner function with a mass of $({3.35}_{- 0.02}^{+ 0.01} \pm 0.02) GeV / c^{2}$ and a width of $({0.07}_{- 0.03}^{+ 0.04} \pm 0.04) GeV / c^{2}$ . We measure its branching fraction to be $({3.9}_{- 0.7}^{+ 0.8} \pm 0.4 \pm 1.0) \times 10^{- 5}$ with a statistical significance of $6.2 σ$ . The errors are statistical, systematic, and that of the $Λ_{c}^{+} \to p K^{-} π^{+}$ decay branching fraction.