Subjects: Physics >> Nuclear Physics submitted time 2023-06-18 Cooperative journals: 《Nuclear Science and Techniques》
Abstract： Nuclear double β--decay with two neutrinos is an important decay mode for some unstable nuclei. Based on the available experimental data of nuclear double β--decay, we propose that there is a law between the logarithm of double β--decay half-lives and the reciprocal of the decay energy. The physics behind the law is discussed and it is found that this is associated with the universal properties of the weak interaction. This double β--decay law is similar to the famous Geiger-Nuttall law of α-decay. The law is applied to predictions of the nuclear double β--decay half-lives for six even-even nuclei from Z=84 to Z=98 and we found that 232Th is very interesting for future experiments. The branching ratios between double β--decay and α-decay are also estimated for the six even-even nuclei and this is useful for future experimental search of new emitters of double β--decay.
Subjects: Physics >> Nuclear Physics submitted time 2023-06-18 Cooperative journals: 《Nuclear Science and Techniques》
Abstract： Recently, we analyze the α-decay data of even-Z nuclei and propose the new Geiger-Nuttall law where the effects of the quantum numbers of α-core relative motion are naturally embedded in the law [Physical Review C 85, 044608 (2012)].In this paper, we firstly test whether the new law without any change of parameters can be applied to the α-decays of odd-Z nuclei which are more complicated than those of even-even nuclei. Then the nuclear shell effect around N=126 is analyzed for very proton-rich nuclei with Z=85–92 based on the data of α-decay energies and half-lives. A long-lived island beyond the stable line is proposed where the half-lives of nuclei on this island are abnormally long. The mechanism of the appearance of the island and its significance to other mass ranges are discussed.
Subjects: Physics >> Nuclear Physics submitted time 2016-08-30
Abstract： We report the neutrino mass hierarchy (MH) sensitivity of medium baseline reactor neutrino experiments with multiple detectors. Sensitivity of determining the MH can be significantly improved by adding a near detector and combining both the near and far detectors. The size of the sensitivity improvement is related to accuracy of the individual mass-splitting measurements and requires strict control on the relative energy scale uncertainty of the near and far detectors. We study the impact of both baseline and target mass of the near detector on the combined sensitivity. A figure-of-merit is defined to optimize the baseline and target mass of the near detector and the optimal selections are ∼13~km and ∼4~kton respectively for a far detector with the 20~kton target mass and 52.5~km baseline. As typical examples of future medium baseline reactor neutrino experiments, the optimal location and target mass of the near detector are selected for JUNO and RENO-50. Finally, we discuss distinct effects of the neutrino spectrum uncertainty for setups of a single detector and double detectors, which indicate that the spectrum uncertainty can be well constrained in the presence of the near detector.
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