Multiple CP non-conserving mechanisms of (ββ)0ν-decay and nuclei with largely different nuclear matrix elements

We investigate the possibility to discriminate between different pairs of CP non-conserving mechanisms inducing the neutrinoless double beta (beta beta)(0 nu)-decay by using data on (beta beta)(0 nu)-decay half-lives of nuclei with largely different nuclear matrix elements (NMEs). The mechanisms studied are: light Majorana neutrino exchange, heavy left-handed (I,I1) and heavy right-handed (RII) Nlajorana neutrino exchanges, lepton charge non-conserving couplings in St5SY theories with R-parity breaking giving rise to the dominant gluino exchange and the squark-neutrino mechanisms. The nuclei considered are Ge-76, Se-82, Mo-100, Te-130 and Xe-136. Four sets of nuclear matrix elements (NMEs) of the decays of these five nuclei, derived within the Self-consistent Renormalized Quasiparticle Random Phase Approximation (SRQRPA), were employed in our analysis. While for each of the five single mechanisms discussed, the NMEs for Ge-76, Se-82, Mo-100, Te-130 differ relatively little, the relative difference between the NMEs of any two nuclei not exceeding 10%, the NMEs for Xe-136 differ significantly from those of Ge-76, Se-82, Mo-100, Te-130, being by a factor similar to(1.3 - 2.5) smaller. This allows, in principle, to draw conclusions about the pair of non-interfering (interfering) mechanisms possibly inducing the (beta beta)(0v)-decay from data on the half-lives of Xe-136 and of at least one (two) more isotope(s) which can be e.g., any of the four, Ge-76, Se-82, Mo-100 and Te-130. Depending On the sets of mechanisms considered, the conclusion can be independent of, or can depend on, the MMEs used in the analysis. The implications of the EXO lower bound on the half-life of Xe-136 for the problem studied are also exploited.