Search for the decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>B</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:mo>→</mml:mo><mml:mi>γ</mml:mi><mml:mi>γ</mml:mi></mml:math>
Bibliographic record
Abstract
We report the result of a search for the rare decay ${B}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ in $426\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data, corresponding to $226\ifmmode\times\else\texttimes\fi{}{10}^{6}$ ${B}^{0}{\overline{B}}^{0}$ pairs, collected on the $\ensuremath{\Upsilon}(4S)$ resonance at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider using the BABAR detector. We use a maximum likelihood fit to extract the signal yield and observe ${21}_{\ensuremath{-}12}^{+13}$ signal events with a statistical significance of $1.8\ensuremath{\sigma}$. This corresponds to a branching fraction $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})=(1.7\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.2(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. Based on this result, we set a 90% confidence level upper limit of $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})<3.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.015 | 0.006 |
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".