The possibility to probe new physics scenarios of light Majorana neutrino exchange and right-handed currents at the planned next generation neutrinoless double β decay experiment SuperNEMO is discussed. Its ability to study different isotopes and track the outgoing electrons provides the means to discriminate different underlying mechanisms for the neutrinoless double β decay by measuring the decay half-life and the electron angular and energy distributions.a

For the first time, limits on double-beta processes in 74 Se have been obtained using a 400 cm 3 HPGe detector and an external source consisting of natural selenium powder. At a confidence level of 90%, they are 1.9 × 10 18 y for the β + EC(0ν + 2ν) transition to the ground state, 7.7 × 10 18 y for the ECEC(2ν) transition to the 2 + 1 excited state in 74 Ge (595.8 keV), 1.1 × 10 19 y for the ECEC(0ν) transition to the 2 + 1 excited state in 74 Ge (595.8 keV) and 5.5 × 10 18 y for the ECEC(2ν) and ECEC(0ν) transitions to the 2 + 2 excited state in 74 Ge (1204.2 keV). The last transition is discussed in association with a possible enhancement of the decay rate, in this case by several orders of magnitude, because the ECEC(0ν) process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such processes in future experiments are discussed. 14.80.Mz PACS