Improved analysis of the rare decay processes of Λ_b

It is noted that in the new Particle Data Group (PDG) version the rare decays of the ${\Lambda }_b$ baryon have been revised with more accuracy. The new results show that most of the existing theoretical results on the process ${\Lambda }_b\to \Lambda \gamma$ are larger than those of experiments. With the improved higher-order light-cone distribution amplitudes of the Λ baryon, we reanalyze the process in the framework of light-cone quantum chromodynamics sum rules and the branching ratio is estimated to be $Br({\Lambda }_b\to \Lambda \gamma )=\left({7.38}_{-0.39}^{+0.40}\right)\times {10}^{-6}$, which is consistent with the new experimental result. Furthermore, another process ${\Lambda }_b\to \Lambda$ $l^{+}{l}^{-}$ is also analyzed in the same frame. The final branching ratio is calculated to be $Br({\Lambda }_b\to \Lambda l^{+}{l}^{-})=1.20\times {10}^{-6}$, which is in good accordance with the data from the PDG and other theoretical predictions. (paper)