Decay angular distributions of K^* and D^* vector mesons in pion-nucleon scattering

The production mechanisms of open strangeness ($K^*$) and open charm ($D^*$) vector mesons in $\pi^- p$ scattering, namely, $\pi^- +p \to K^{*0} + \Lambda$ and $\pi^- + p \to D^{*-} + \Lambda_c^+$, are investigated within the modified quark-gluon string model. In order to identify the major reaction mechanisms, we consider the subsequent decays of the produced vector mesons into two pseudoscalar mesons, i.e., $K^* \to K + \pi$ and $D^* \to D + \pi$. We found that the decay distributions and density matrix elements are sensitive to the production mechanisms and can be used to disentangle the vector trajectory and pseudoscalar trajectory exchange models. Our results for $K^*$ production are compared with the currently available experimental data and the predictions for $D^*$ production processes are presented as well. Our predictions can be tested at the present or planned experimental facilities.