Neutrinoless double beta decay (0νββ) is potentially the best resource to probe the Majorana or Dirac nature of neutrino and to extract its effective mass. Moreover, if observed, 0νββ will signal that the total lepton number is not conserved. Presently, this physics case is one of the most important researches “beyond the Standard Model” and might guide the way toward a Grand Unified Theory of fundamental interactions.

Since the ββ decay process involves transitions in atomic nuclei, nuclear structure issues must be accounted for to describe it. The 0νββ decay rate 1/[T1/2] can be factorized as a phase-space factor G0ν, the nuclear matrix element (NME) M_0ν and a term f(mi,Uei) containing the masses mi and the mixing coefficients Uei of the neutrino species. Thus, if the NMEs are established with sufficient precision, the neutrino masses and the mixing coefficients can be extracted from 0νββ decay rate measurements.

NUMEN is an innovative technique to access the nuclear matrix elements entering the expression of the life time of the double beta decay by relevant cross sections of double charge exchange reactions.

A key aspect of the project is the use of the K800 Superconducting Cyclotron (CS) for the acceleration of the required high resolution and low emittance heavy-ion beams and of the MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles. The use of the high-order trajectory reconstruction technique, implemented in MAGNEX, allows to reach the high mass, angular and energy resolution required even at very low cross section. The LNS set-up is today an ideal one for this research even at a worldwide perspective. However a main limitation on the beam current delivered by the accelerator and the maximum rate accepted by the MAGNEX focal plane detector must be sensibly overcome in order to systematically provide accurate numbers to the neutrino physics community in all the studied cases. The upgrade of the LNS facilities in this view is part of this project.