Highlights
• The Δ mass dependence of the M matrix and its influence on the ${{N\Delta \to NN}}$ cross-sections
2020, 44(2): 024106. doi: 10.1088/1674-1137/44/2/024106
The $\Delta$ mass dependence of the M matrix and its influence on the $N\Delta \to NN$ cross-sections are investigated in the one-boson exchange model. Our calculations show that the $\Delta$ mass dependence of the momentum of the outgoing $\Delta$ and the M matrix affects the calculations of $\sigma_{N\Delta\to NN}$, especially around the threshold energy.
• Measurement of ${{\varXi_{cc}^{++}}}$ production in pp collisions at ${\sqrt{ s}=13}$ TeV
2020, 44(2): 022001. doi: 10.1088/1674-1137/44/2/022001
The production of $\varXi _{cc}^ {++}$ baryons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=13\;{\rm{TeV}}$ is measured in the transverse-momentum range $4 < p_{\rm{T}} <15\;{\rm{GeV}}/c$ and the rapidity range $2.0 <y <4.5$. The data used in this measurement correspond to an integrated luminosity of $1.7\;{\rm{fb}}^{-1}$, recorded by the LHCb experiment during 2016. The ratio of the $\varXi _{cc}^ {++}$ production cross-section times the branching fraction of the $\varXi _{cc}^ {++} \to \varLambda _c^ + K^-\pi^+ \pi^+$ decay relative to the prompt $\varLambda _c^ +$ production cross-section is found to be $(2.22\pm 0.27 \pm 0.29)\times 10^{-4}$, assuming the central value of the measured $\varXi _{cc}^ {++}$ lifetime, where the first uncertainty is statistical and the second systematic.
• Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment
2020, 44(2): 021001. doi: 10.1088/1674-1137/44/2/021001
From April to July 2018, a data sample at the peak energy of the $\varUpsilon \left( {4{\rm{S}}} \right)$ resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be ($496.3 \pm 0.3 \pm 3.0)\;{\rm pb}^{-1}$, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.
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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.
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2020 Vol. 44, No. 2
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IF: 5.861

Monthly founded in 1977

ISSN 1674-1137 CN 11-5641/O4

Original research articles, Ietters and reviews Covering theory and experiments in the fieids of

• Particle physics
• Nuclear physics
• Particle and nuclear astrophysics
• Cosmology
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