Measurements of ${\cal B}(\bar{B}^0 \to \Lambda_{c}^{+} \bar{p})$ and ${\cal B}(B^- \to \Lambda_{c}^{+} \bar{p} \pi^-)$ and Studies of $\Lambda_{c}^{+}\pi^-$ Resonances

TL;DR

This paper measures branching fractions of specific B meson decays involving charm baryons, observes new resonant states, and confirms the spin of a known baryon, providing insights into baryonic decay dynamics and excited charm states.

Contribution

It reports the first observation of the $B^- o ext{Sigma}_c(2800)^0 ar{p}$ decay and measures the spin of $ ext{Sigma}_c(2455)^0$, advancing understanding of baryonic B decays and charm baryon spectroscopy.

Findings

Measured branching ratio ${ m rac{B^- o ext{Lambda}_c^+ ar{p} ext{pi}^-}{ar{B}^0 o ext{Lambda}_c^+ ar{p}}} = 15.4 \

Observed $ar{B}^- o ext{Sigma}_c(2455)^0 ar{p}$ and $ ext{Sigma}_c(2800)^0 ar{p}$ decays

Determined the spin of $ ext{Sigma}_c(2455)^0$ to be 1/2

Abstract

We present an investigation of the decays $\bar{B}^0 \to \Lambda_{c}^{+} \bar{p}$ and $B^- \to \Lambda_{c}^{+} \bar{p} \pi^-$ based on $383\times10^6$ $\Upsilon(4S) \to B\bar{B}$ decays recorded with the BABAR detector. We measure the branching fractions of these decays; their ratio is ${\cal B}(B^- \to \Lambda_{c}^{+} \bar{p} \pi^-) / {\cal B}(\bar{B}^0 \to \Lambda_{c}^{+} \bar{p}) = 15.4 \pm 1.8 \pm 0.3$. The $B^- \to \Lambda_{c}^{+} \bar{p} \pi^-$ process exhibits an enhancement at the $\Lambda_{c}^{+} \bar{p}$ threshold and is a laboratory for searches for excited charm baryon states. We observe the resonant decays $\bar{B}^- \to \Sigma_{c}(2455)^{0} \bar{p}$ and $B^- \to \Sigma_{c}(2800)^{0} \bar{p}$ but see no evidence for $B^- \to \Sigma_{c}(2520)^{0} \baver{p}$. This is the first observation of the decay $B^- \to \Sigma_{c}(2800)^{0} \bar{p}$; however, the mass of the observed excited $\Sigma_{c}^{0}$ state is $(2846\pm8\pm10)MeV/c^2$, which is somewhat inconsistent with previous measurements. Finally, we examine the angular distribution of the $B^- \to \Sigma_{c}(2455)^{0} \bar{p}$ decays and measure the spin of the $\Sigma_{c}(2455)^{0}$ baryon to be 1/2, as predicted by the quark model.