Majorana parameters of the interacting boson model of nuclear structure and their implication for 0νββ decay
The well-known spherical-deformed-transitional nucleus and potential 0νββemitter Nd150and its daughter Sm150were investigated in nuclear resonance fluorescence experiments using quasimonoenergetic, linearly polarized γ-ray beams. For both nuclei transitions from the 1+ scissors mode to the 02+ and 22+ 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 Nd150→Sm150 0νββdecay in the IBM-2 with these improved representations results in MIBM-2(0νββ)[01+]=3.35 for the NME for 0νββdecay into the ground state of Sm150and MIBM-2(0νββ)[02+]=1.30 for 0νββdecay to its 02+ state.