Dominance of pion exchange in R-parity-violating supersymmetric contributions to neutrinoless double beta decay

We present a new contribution of the R-parity-violating (R-p) supersymmetry (SUSY) to neutrinoless double beta decay (O nu beta beta) via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R-p SUSY interactions. We have found this pion-exchange mechanism to dominate over the conventional two-nucleon one. The latter corresponds to direct interaction between quarks from two decaying neutrons without any light hadronic mediator like pi meson. The constraints on the certain R-p SUSY parameters are extracted from the current experimental O nu beta beta-decay half-life limit. These constraints are significantly stronger than those previously known or expected from the ongoing accelerator experiments.