2018 Fiscal Year Research-status Report
Nuclear structure to unveil the nature of neutrinos and dark matter
| Project/Area Number |
18K03639
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Menendez Javier 東京大学, 大学院理学系研究科(理学部), 特任研究員 (70807635)
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| Project Period (FY) |
2018-04-01 – 2020-03-31
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| Keywords | Double-beta decay / Double electron capture / Dark matter scattering / Meson-exchange current |
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| Outline of Annual Research Achievements |
In FY2018 we have accomplished the following main achievements:
* First determination of the coupling of a dark matter particle (WIMP) to a pion exchanged by two nucleons of a xenon nucleus. The study was performed in a joint theory-experiment article together with the XENON collaboration, and was published in the journal Physical Review Letters.
* Extension of general spin-independent dark matter scattering off nuclei, considering fluorine, silicon, argon and germanium, therefore covering all nuclei (in addition to xenon, studied in previous work), used as targets in dark matter direct detection experiments. The study was published in the journal Physical Review D.
* First shell model prediction of the two-neutrino double electron capture nuclear matrix element of xenon-124, submitted for publication. Our theoretical prediction was subsequently found in very good agreement with an experimental measurement by the XENON collaboration.
* Comparison of the electron spectrum of xenon-136 double-beta decay with precision experimental data. The shell model prediction is consistent with the limits set by the precision analysis of the KamLAND-Zen collaboration. The study has been accepted for publication in the journal Physical Review Letters.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The research is progressing more smoothly than initially planned. In FY2018 the main goals for the study of the interaction of dark matter particles with nuclei have been achieved. We have extended the calculation of the nuclear structure factors describing the interaction of dark matter particles (WIMPs) to nuclei to argon, fluorine, silicon and germanium. In addition, the first determination of the coupling of WIMPs to a pion was determined for a xenon nucleus, in joint work with the XENON collaboration.
On double-beta decay, we have obtained the first shell model prediction of the matrix element of the double electron capture of xenon-124. The theoretical prediction was confirmed in good agreement with a subsequent measurement. In addition, we have compared the electron spectrum of the double-beta decay of xenon-136 to a recent precision experimental analysis by the KamLAND-Zen collaboration.
As a result, we will publish two works in the journal Physical Review Letters, and one work in Physical Review D. Another work has been submitted for publication.
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| Strategy for Future Research Activity |
In FY2019 the plan is to focus on nuclear structure ab initio calculations to prepare for the computation of nuclear matrix elements of neutrinoless double-beta decay for first principles.
In addition, I plan to focus on the study of correlations of double-beta decay with other nuclear properties, such as double Gamow-Teller and double-gamma transitions.
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