Diffractive Lambda_c^+ Productions in Polarized pp Reactions and Polarized Gluon Distribution

To test the model of the polarized gluon distribution $\Delta G(x, Q^2)$ in the proton, we propose a new process, diffractive $\Lambda_c^+$ productions in polarized $pp$ reactions, which will be observed in the forthcoming RHIC and also the proposed HERA-$\vec {\rm N}$ experiments. The spin correlation between the target proton and the $\Lambda_c^+$ produced in the target fragmentation region largely depends on $\Delta G(x, Q^2)$ and thus, the process is quite promising for testing the models of $\Delta G(x, Q^2)$.