First Search for Exotic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math>Boson Decays into Photons and Neutral Pions in Hadron Collisions
Bibliographic record
Abstract
A search for forbidden and exotic $Z$ boson decays in the diphoton mass spectrum is presented for the first time in hadron collisions, based on data corresponding to $10.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity from proton-antiproton collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ collected by the CDF experiment. No evidence of signal is observed, and 95% credibility level Bayesian upper limits are set on the branching ratios of decays of the $Z$ boson to a photon and neutral pion (which is detected as a photon), a pair of photons, and a pair of neutral pions. The observed branching ratio limits are $2.01\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ for $Z\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$, $1.46\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ for $Z\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$, and $1.52\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ for $Z\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$. The $Z\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ and $Z\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ limits improve the most stringent results from other experiments by factors of 2.6 and 3.6, respectively. The $Z\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ branching ratio limit is the first experimental result on this decay.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".