Heavy-ion double charge exchange reactions: A tool toward 0 νββ nuclear matrix elements

The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial- and final-state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the ⁴⁰Ca(¹⁸O,¹⁸Ne)⁴⁰Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0⁺ → 0⁺ transition to ⁴⁰Ar_gs, at least at very forward angles. (orig.)