Transfer Reactions Between Odd-Odd and Even-Even Nuclei by Using the Interacting Boson Fermion Fermion Model and 0νββ Decay in Closure Approximation

Spectroscopic amplitudes (SAs) in the interacting boson fermion fermion model (IBFFM) are necessary for the computation of 0400 decay but also for cross sections of heavy-ion reactions, in particular, double charge exchange reactions for the NUMEN Collaboration, if one does not want to use the closure limit. We present for the first time (i) the formalism and operators to compute in a general case the spectroscopic amplitudes in the IBFFM scheme from even-even to odd-odd nuclei, in a way suited to be used in reaction code, i.e., extracting the contribution of each orbital; (2) the odd-odd nuclei as described by the old IBFFM are obtained for the first time with the new implementation of machine learning (ML) techniques for fitting the parameters, getting a more realistic description. The one-body transition densities for 116Cd -> 116In and 116In -> 116Sn are part of the experimental program of the NUMEN experiment, which aims to find constraints on 0400 decay matrix elements. As a first application of the spectroscopic amplitudes we present the calculation of the 0400 nuclear matrix elements in the IBFFM formalism in closure approximation.