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Large-Scale Shell-Model Analysis of the Neutrinoless ββ Decay of ^{48}Ca
Y Iwata1, N Shimizu1, T Otsuka1,2,3,4
1Center for Nuclear Study, The University of Tokyo, 113-0033 Tokyo, Japan.
Physical Review Letters
|April 2, 2016
Summary
We calculated the nuclear matrix element for neutrinoless double-beta decay in Calcium-48. Including sd-pf shell excitations significantly enhances this element, reducing the decay lifetime.
Area of Science:
- Nuclear Physics
- Particle Physics
- Quantum Chemistry
Background:
- Neutrinoless double-beta decay is a hypothetical process.
- Understanding this decay requires accurate nuclear matrix element calculations.
- Calcium-48 is a key isotope for studying this decay.
Purpose of the Study:
- To calculate the nuclear matrix element for the neutrinoless double-beta decay of Calcium-48.
- To investigate the impact of including sd and pf shells in shell-model calculations.
- To explore implications for other potential neutrinoless double-beta decay candidates.
Main Methods:
- Large-scale shell-model calculations.
- Inclusion of two harmonic oscillator shells (sd and pf).
- Comparison with experimental data for excitation spectra and two-neutrino double-beta decay.
Main Results:
- Accurate reproduction of excitation spectra for Calcium-48 and Titanium-48.
- Good agreement with experimental data for two-neutrino double-beta decay of Calcium-48.
- A 30% enhancement of the neutrinoless double-beta decay nuclear matrix element compared to pf-shell calculations.
- A reduction in the decay lifetime by almost a factor of 2.
Conclusions:
- Pairing correlations from cross-shell sd-pf excitations are crucial for enhancing the matrix element.
- The enhanced matrix element significantly shortens the predicted decay lifetime.
- Findings provide insights for searches in heavier isotopes.
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