Heavy to light baryon transition form factors

Recently, Stech found form factor relations for heavy to light transitions based on two simple dynamical assumptions for spectator partical. In this work we generalize his approach to the case of baryons and find that for $\Lambda_{Q}\to\Lambda$ ($Q=b$ or $c$) only one independent form factor remains in limit $m_{Q}\to\infty$. Furthermore, combining with the model of Guo and Kroll we determine both of the two form factors for $\Lambda_{Q}\to\Lambda$ in the heavy quark limit. The results are applied to $\Lambda_{b}\to\Lambda + J/\psi$ which is not clarified both theoretically and experimentally. It is found that the branching ratio of $\Lambda_{b}\to\Lambda + J/\psi$ is of order 10^{-5}.