High-precision branching-ratio measurement for the superallowed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>β</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>emitter<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow/><mml:mn>74</mml:mn></mml:msup></mml:math>Rb
Bibliographic record
Abstract
A high-precision branching-ratio measurement for the superallowed ${\ensuremath{\beta}}^{+}$ decay of ${}^{74}$Rb was performed at the TRIUMF Isotope Separator and Accelerator (ISAC) radioactive ion-beam facility. The scintillating electron-positron tagging array (SCEPTAR), composed of 10 thin plastic scintillators, was used to detect the emitted $\ensuremath{\beta}$ particles; the 8$\ensuremath{\pi}$ spectrometer, an array of 20 Compton-suppressed HPGe detectors, was used for detecting $\ensuremath{\gamma}$ rays that were emitted following Gamow-Teller and nonanalog Fermi ${\ensuremath{\beta}}^{+}$ decays of ${}^{74}$Rb; and the Pentagonal Array of Conversion Electron Spectrometers (PACES), an array of 5 Si(Li) detectors, was employed for measuring $\ensuremath{\beta}$-delayed conversion electrons. Twenty-three excited states were identified in ${}^{74}$Kr following $8.241(4)\ifmmode\times\else\texttimes\fi{}{10}^{8}$ detected ${}^{74}$Rb $\ensuremath{\beta}$ decays. A total of 58 $\ensuremath{\gamma}$-ray and electron transitions were placed in the decay scheme, allowing the superallowed branching ratio to be determined as ${B}_{0}=99.545(31)%$. Combined with previous half-life and $Q$-value measurements, the superallowed branching ratio measured in this work leads to a superallowed $ft$ value of 3082.8(65) s. Comparisons between this superallowed $ft$ value and the world-average-corrected $\overline{\mathcal{F}t}$ value, as well as the nonanalog Fermi branching ratios determined in this work, provide guidance for theoretical models of the isospin-symmetry-breaking corrections in this mass region.
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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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.011 | 0.004 |
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".