Rare decays of $\Lambda_b$ baryons in a quark model

The exclusive rare decays $\Lambda_b \rightarrow \Lambda^{(*)}\gamma$ and $\Lambda_b \rightarrow \Lambda^{(*)}\ell^{+}\ell^{-}$ are treated in the framework of a constituent quark model. By use of single component wavefunctions, the hadronic form factors for the vector, axial vector and tensor currents are derived analytically. The decay rates and forward-backward asymmetries are calculated with and without charmonium resonance contributions for the dileptonic decays. The branching ratios for these decays are also reported.