Measurement of the forward–backward asymmetry of top-quark and antiquark pairs using the full CDF Run II data set
Bibliographic record
Abstract
We measure the forward--backward asymmetry of the production of top-quark and antiquark pairs in proton-antiproton collisions at center-of-mass energy $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ using the full data set collected by the Collider Detector at Fermilab (CDF) in Tevatron Run II corresponding to an integrated luminosity of $9.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The asymmetry is characterized by the rapidity difference between top quarks and antiquarks ($\mathrm{\ensuremath{\Delta}}y$) and measured in the final state with two charged leptons (electrons and muons). The inclusive asymmetry, corrected to the entire phase space at parton level, is measured to be ${A}_{\mathrm{FB}}^{t\overline{t}}=0.12\ifmmode\pm\else\textpm\fi{}0.13$, consistent with the expectations from the standard model (SM) and previous CDF results in the final state with a single charged lepton. The combination of the CDF measurements of the inclusive ${A}_{\mathrm{FB}}^{t\overline{t}}$ in both final states yields ${A}_{\mathrm{FB}}^{t\overline{t}}=0.160\ifmmode\pm\else\textpm\fi{}0.045$, which is consistent with the SM predictions. We also measure the differential asymmetry as a function of $\mathrm{\ensuremath{\Delta}}y$. A linear fit to ${A}_{\mathrm{FB}}^{t\overline{t}}(|\mathrm{\ensuremath{\Delta}}y|)$, assuming zero asymmetry at $\mathrm{\ensuremath{\Delta}}y=0$, yields a slope of $\ensuremath{\alpha}=0.14\ifmmode\pm\else\textpm\fi{}0.15$, consistent with the SM prediction and the previous CDF determination in the final state with a single charged lepton. The combined slope of ${A}_{\mathrm{FB}}^{t\overline{t}}(|\mathrm{\ensuremath{\Delta}}y|)$ in the two final states is $\ensuremath{\alpha}=0.227\ifmmode\pm\else\textpm\fi{}0.057$, which is $2.0\ensuremath{\sigma}$ larger than the SM prediction.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".