Majorana parameters of the interacting boson model of nuclear structure and their implication for 0 nu beta beta decay

The well-known spherical-deformed-transitional nucleus and potential 0 nu beta beta emitter Nd-150 and its daughter Sm-150 were investigated in nuclear resonance fluorescence experiments using quasimonoenergetic, linearly polarized gamma-ray beams. For both nuclei transitions from the 1(+) scissors mode to the 0(2)(+) and 2(2)(+) states were observed for the first time and their respective M1 transition strengths were determined. Through a systematic investigation, a sensitivity of these transition strengths to the three Majorana parameters of the interacting boson model-2 (IBM-2) was established. In combination with the novel experimental data, this poses strong constraints to the Majorana parameters in improved IBM-2 representations of both nuclei. A subsequent recalculation of the nuclear matrix elements (NMEs) for the Nd-150 -> Sm-150 0 nu beta beta decay in the IBM-2 with these improved representations results in M-IBM-2((0)nu beta beta) [0(1)(+)] = 3.35 for the NME for 0 nu beta beta decay into the ground state of Sm-150 and M-IBM-2((0)nu(beta beta)) [0(2)(+)] = 1.30 for 0 nu beta beta decay to its 0(2)(+) state.