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  • Measurement of 85Rb(n, 2n)84Rb reaction cross-section from 12 MeV up to 19.8 MeV
    Published: 2020-01-22, doi: 10.1088/1674-1137/44/3/034001
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    The cross-section data of the 85Rb(n, 2n)84Rb reaction have been measured with the neutron energies of 12 MeV to 19.8 MeV using the activation technique and the relative method. The 85Rb samples were irradiated on the surface of a two-ring orientation assembly with neutrons produced from the 3H(d, n)4He reaction at the 5SDH-2 1.7-MV Tandem accelerator in China. Theoretical model calculations were performed with the TALYS-1.9 code. The present data were compared with previously obtained experimental data and the available evaluated data.
  • Towards the meV limit of the effective neutrino mass in neutrinoless double-beta decays
    Published: 2020-01-22, doi: 10.1088/1674-1137/44/3/033103
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    We emphasize that it is extremely important for future neutrinoless double-beta ($0\nu\beta\beta$) decay experiments to reach the sensitivity to the effective neutrino mass $|m_{\beta\beta}| \approx 1\;{\rm {meV}}$. With such a sensitivity, it is highly possible to discover the signals of $0\nu\beta\beta$ decays. If no signal is observed at this sensitivity level, then either neutrinos are Dirac particles or stringent constraints can be placed on their Majorana masses. In this paper, assuming the sensitivity of $|m_{\beta\beta}| \approx 1\;{\rm {meV}}$ for future $0\nu\beta\beta$ decay experiments and the precisions on neutrino oscillation parameters after the JUNO experiment, we fully explore the constrained regions of the lightest neutrino mass $m_1$ and two Majorana-type CP-violating phases $\{\rho, \sigma\}$. Several important conclusions in the case of normal neutrino mass ordering can be made. First, the lightest neutrino mass is severely constrained to a narrow range $m_1 \in [0.7, 8]\;{\rm {meV}}$, which together with the precision measurements of neutrino mass-squared differences from oscillation experiments completely determines the neutrino mass spectrum $m_2 \in [8.6, 11.7]\;{\rm {meV}}$ and $m_3 \in [50.3, 50.9]\;{\rm {meV}}$. Second, one of the two Majorana CP-violating phases is limited to $\rho \in [130^\circ, 230^\circ]$, which cannot be obtained from any other realistic experiments. Third, the sum of three neutrino masses is found to be $\Sigma \equiv m_1 + m_2 + m_3 \in [59.2, 72.6]\;{\rm {meV}}$, while the effective neutrino mass for beta decays turns out to be $m_\beta \equiv (|U_{e1}|^2 m^2_1 + |U_{e2}|^2 m^2_2 + |U_{e3}|^2 m^2_3)^{1/2}\in [8.9, 12.6]\;{\rm {meV}}$. These observations clearly set up the roadmap for future non-oscillation neutrino experiments aiming to solve the fundamental problems in neutrino physics.
  • High-K multi-particle bands and pairing reduction in 254No
    Published: 2020-01-19, doi: 10.1088/1674-1137/44/3/034106
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    The multi-particle states and rotational properties of the two-particle bands in $^{254}{\rm{No}}$ are investigated by the cranked shell model with pairing correlations treated by the particle number conserving method. The rotational bands on top of the two-particle $K^{\pi}=3^+, \;8^-$ and $10^+$ states and the pairing reduction are studied theoretically in $^{254}{\rm{No}}$ for the first time. The experimental excitation energies and moments of inertia of the multi-particle states are reproduced well by the calculations. Better agreement with the data is achieved by including the high-order deformation $\varepsilon_{6}$, which leads to enlarged $Z=100$ and $N=152$ deformed shell gaps. An increase of $J^{(1)}$ in these two-particle bands compared with the ground state band is attributed to the pairing reduction due to the Pauli blocking effect.