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Neutrino-less double beta decay with SuperNEMO

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In particle physics the fermions could be either Dirac or Majorana but no evidence of Majorana particles has been found yet. Since neutrino is a neutral fermion it is a good candidate to be a Majorana particle. In this case the neutrino-less double beta decay will be allowed and its observation will have interesting implication for particle physics.

The Neutrino Ettore Majorana Observatory (NEMO) collaboration is building SuperNEMO, a new detector based on the technology already adopted with success by the NEMO3 experiment. This technique consists of a thin foil of double beta emitter sandwiched between a tracking chamber (to reconstruct the electron tracks), and a calorimeter (to measure the electron energies). If compared to other experiments in the domain, SuperNEMO has the unique capability to measure not only the energy of the two emitted electrons, but also to reconstruct the full kinematic of the events thanks to the tracker. This knowledge allows reducing the backgrounds associated to the search of low energy electron. Moreover, in case of discovery of the neutrino-less double beta decay, the study of the electron kinematics could clarify the mechanism beyond such process. The detector will be made of 20 independent modules measuring 100 kg of 82Se. The proposed sensitivity of T0ν1/2 > 1026 yr. (mν < 0.04 - 0.11 eV) is competitive with other experiments, but it is nonetheless challenging with the adopted technology. In order to demonstrate the feasibility of the full experiment, the first step of SuperNEMO is the construction in the Modane Underground Laboratory (LSM) of a first demonstrator module containing 7 kg of 82Se. The goal is to meet the very stringent constraint of 10-4 cts./(keV kg y) on the background, mainly due to the contamination of the detector components in 208Tl and 214Bi. With an expected sensitivity of T0ν1/2 > 6.6 1024 yr. (mν < 0.2 - 0.4 eV) after 2.5 years, the demonstrator module will also be able to perform a competitive measurement.

The LAPP neutrino group is involved in the construction of the demonstrator module and is responsible for the production of the 82Se foil source and the development of the slow control system.