Search for Lepton-Flavor Violation in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi></mml:mrow></mml:math>-Boson Decays with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>τ</mml:mi></mml:math> Leptons with the ATLAS Detector
Bibliographic record
Abstract
A search for lepton-flavor-violating $Z\ensuremath{\rightarrow}e\ensuremath{\tau}$ and $Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau}$ decays with $pp$ collision data recorded by the ATLAS detector at the LHC is presented. This analysis uses $139\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of Run 2 $pp$ collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$ and is combined with the results of a similar ATLAS search in the final state in which the $\ensuremath{\tau}$ lepton decays hadronically, using the same data set as well as Run 1 data. The addition of leptonically decaying $\ensuremath{\tau}$ leptons significantly improves the sensitivity reach for $Z\ensuremath{\rightarrow}\ensuremath{\ell}\ensuremath{\tau}$ decays. The $Z\ensuremath{\rightarrow}\ensuremath{\ell}\ensuremath{\tau}$ branching fractions are constrained in this analysis to $\mathcal{B}(Z\ensuremath{\rightarrow}e\ensuremath{\tau})<7.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}(Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau})<7.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ at 95% confidence level. The combination with the previously published analyses sets the strongest constraints to date: $\mathcal{B}(Z\ensuremath{\rightarrow}e\ensuremath{\tau})<5.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}(Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau})<6.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ at 95% confidence level.
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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 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 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".