Constraints on R-parity violating interactions in supersymmetric standard model from leptonic decays of D_s and B^+ mesons

We study leptonic decays D_s\to \tau \nu and B^+ \to \tau \nu in R-parity violating (RPV) supersymmetric standard model. The interference between the s-channel slepton exchange and the t-channel squark exchange diagrams could be destructive in a certain model parameter region so that sizable RPV couplings are allowed. Contributions from the RPV interactions to the final states with the lepton flavor violation (LFV), \tau\nu_\mu (\tau \nu_e), are also examined taking account of constraints on the RPV couplings from the other LFV processes.