Parameter dependence of the β-decay properties of neutron-rich Zr isotopes within the interacting boson model

We investigate parameter dependence of the calculated β-decay properties, as well as low-lying states for the neutron-rich Zr isotopes within the neutron-proton interacting boson model (IBM-2) and interacting boson-fermion-fermion model (IBFFM-2). It is shown that the calculated log₁₀ft values for the transitions of the 0⁺₁ ground states of the parent even-even nuclei ⁹⁶⁻¹⁰²Zr into the 1⁺₁ states of the daughter odd-odd nuclei ⁹⁶⁻¹⁰²Nb consistently exhibit a strong dependence on those parameters associated with the quadrupole-quadrupole boson interaction, and with the residual interaction between an unpaired neutron and an unpaired proton in the IBFFM-2 Hamiltonian for the odd-odd Nb nuclei. By the reduction in magnitude of the quadrupole-quadrupole interaction strength by approximately a factor of 2, the calculated log₁₀ft values for the Zr(0⁺₁)→Nb(1⁺₁) transitions increase and agree with the experimental values. This points to a significant improvement over the previous study performed in the same mass region, that consists of the mapping from a relativistic energy density functional calculation onto the IBM-2 Hamiltonian.