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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.001 |
| Meta-epidemiology (narrow) | 0.003 | 0.003 |
| Meta-epidemiology (broad) | 0.002 | 0.005 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.004 | 0.002 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.005 | 0.004 |
| Research integrity | 0.002 | 0.005 |
| Insufficient payload (model declined to judge) | 0.002 | 0.011 |
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; both teacher heads agree on what is shown here.
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".