Low-energy test of second-class current in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>decays of spin-aligned<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow/><mml:mn>20</mml:mn></mml:msup></mml:math>F and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow/><mml:mn>20</mml:mn></mml:msup></mml:math>Na
Bibliographic record
Abstract
The $G$-parity-violating, second-class current- (SCC) induced tensor term in the weak-nucleon axial-vector current was determined from $\ensuremath{\beta}$-decay correlation measurements of the mass $A$ = 20 mirror pair. The alignment correlation terms in the $\ensuremath{\beta}$-decay angular distribution from the purely spin aligned mirror pair, ${}^{20}$F and ${}^{20}$Na, were measured in the present study. Combining the present results with existing results of $\ensuremath{\beta}$ and delayed $\ensuremath{\gamma}$-ray angular correlation measurements for the $A$ = 20 mirror pair, the SCC-induced tensor term was extracted to be ${d}_{\mathit{II}}/Ac$ = 0.18 $\ifmmode\pm\else\textpm\fi{}$ 0.48. In the extraction, the weak-magnetism term, $b/Ac$ = 8.58 $\ifmmode\pm\else\textpm\fi{}$ 0.28, evaluated from the $M$1 analog $\ensuremath{\gamma}$-ray decay strength, was used in a framework of the conserved vector current hypothesis. This is the first unambiguous extraction of the $(b\ensuremath{-}{d}_{\mathit{II}})/Ac$ term free from the contribution of the second-forbidden form factor, ${j}_{2}$, in the axial-vector current, which was a limiting factor for accurate determination of nonexistence of the SSC in the $\ensuremath{\beta}$ decay of the $A$ = 20 system.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.032 | 0.002 |
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".