On the discrimination of different mechanisms for 0ν2β decay

Nuclear matrix elements (NME) for 0νββ decay are calculated in four candidate nuclei (76Ge, 82Se, 100Mo, 130Te) within the quasiparticle random phase approximation (QRPA) and its variants. We assume up to four coexisting mechanisms for 0ν2β decay, mediated by light Majorana neutrino exchange (ν), heavy Majorana neutrino exchange (N), R‐parity breaking supersymmetry (R/), and squark‐neutrino (q), interfering either constructively or destructively with each other. With simple algebraic techniques we show that, by changing the NME within the QRPA variants, the relative contribution of each mechanism to the decay amplitude changes dramatically, even assuming accurate measurements of decay lifetimes. As a consequence, the considered 0νββ mechanisms are nearly degenerate from a phenomenological viewpoint. We discuss implications of such degeneracy on prospective searches for absolute neutrino masses.