Exclusive Rare Decays of Heavy Baryons to Light Baryons: $Λ_b \ri ghtarrow Λγ$ and $Λ_b \to Λl^{+} l^{-}$

Abstract

Rare decays $Λ_b \to Λγ$ and $Λ_b \to Λl^{+} l^{-}$ (l= e, $μ$) are examined. We use QCD sum rules to calculate the hadronic matrix elements governing the decays. The $Λ$ polarization in the decays is analyzed and it is shown that the polarization parameter in $Λ_b \to Λγ$ does not depends on the values of hadronic form factors. And the energy spectrum of $Λ$ in $Λ_b \to Λl^{+} l^{-}$ is given.