Dominance of Pion-exchange in R-parity Violating Supersymmetry   Contributions to Neutrinoless Double Beta Decay
  We present a new contribution of the R-parity violating supersymmetry (SUSY) to neutrinoless double beta decay via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R-parity violating 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 pion. The constraints on the certain R-parity violating SUSY parameters are extracted from the current experimental neutrinoless double beta decay half-life limit. These constraints are significantly stronger than those previously known or expected from the ongoing accelerator experiments. 
Amand Faessler, Sergey Kovalenko, Fedor Simkovic, and Joerg Schwieger