The decay of $\Lambda_b\rightarrow p~K^-$ in QCD factorization approach
  With only the tree level operator, the decay of $\Lambda_b\rightarrow pK$ is predicted to be one order smaller than the experimental data. The QCD penguin effects should be taken into account. In this paper, we explore the one-loop QCD corrections to the decay of $\Lambda_b\to pK$ within the framework of QCD factorization approach. For the baryon system, the diquark approximation is adopted. The transition hadronic matrix elements between $\Lambda_b$ and $p$ are calculated in the light front quark model. The branching ratio of $\Lambda_b\rightarrow pK$ is predicted to be about $4.85\times 10^{-6}$ which is consistent with experimental data $(4.9\pm 0.9)\times 10^{-6}$. The CP violation is about 5\% in theory. 
Jie Zhu, Hong-Wei Ke, Zheng-Tao Wei
hep-ph