<i>Ab Initio</i> Neutrinoless Double-Beta Decay Matrix Elements for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ca</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>48</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ge</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>76</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Se</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>82</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
Bibliographic record
Abstract
We calculate basis-space converged neutrinoless $\ensuremath{\beta}\ensuremath{\beta}$-decay nuclear matrix elements for the lightest candidates: $^{48}\mathrm{Ca}$, $^{76}\mathrm{Ge}$, and $^{82}\mathrm{Se}$. Starting from initial two- and three-nucleon forces, we apply the ab initio in-medium similarity renormalization group to construct valence-space Hamiltonians and consistently transformed $\ensuremath{\beta}\ensuremath{\beta}$-decay operators. We find that the tensor component is non-negligible in $^{76}\mathrm{Ge}$ and $^{82}\mathrm{Se}$, and the resulting nuclear matrix elements are overall 25%--45% smaller than those obtained from the phenomenological shell model. While a final matrix element with uncertainties still requires substantial developments, this work nevertheless opens a path toward a true first-principles calculation of neutrinoless $\ensuremath{\beta}\ensuremath{\beta}$ decay in all nuclei relevant for ongoing large-scale searches.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.004 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.341 | 0.146 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".