Search for dark gauge bosons decaying into displaced lepton-jets in proton–proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
Bibliographic record
Abstract
The dark photon (A'), the gauge boson carrier of a hypothetical new force, has been proposed in a wide range of Beyond the Standard Model (BSM) theories, and could serve as our window to an entire dark sector. A massive A' could decay back to the Standard Model (SM) with a significant branching fraction, through kinetic mixing with the SM photon. If this A' can be produced from decays of a dark scalar that mixes with the SM Higgs boson, collider searches involving leptonic final states provide promising discovery prospects with rich phenomenology. This work presents the results of a search for dark photons in the mass range $0.2 \lesssim m_{A'} \lesssim 10$ GeV decaying into collimated jets of light leptons and mesons, so-called “lepton-jets”. It employs 3.57 fb ${^-1}$ of data from proton-proton collisions at a centre-of-mass energy of √s= 13 TeV, collected during 2015 with the ATLAS detector at the LHC. No deviations from SM expectations are observed. Limits on benchmark models predicting Higgs boson decays to A′ s are derived as a function of the A′ lifetime; limits are also established in the parameter space of mA′ vs. kinetic mixing parameter $\epsilon$. These extend the limits obtained in a similar search previously performed during Run 1 of the LHC, to include dark photon masses $2 \lesssim m_{A'} \lesssim 10$ GeV and to cover higher $\epsilon$ values for $0.2 \lesssim m_{A'} \lesssim 2$ GeV, and are complementary to various other ATLAS A′ searches. As data-taking continues at the LHC, the reach of lepton-jet analyses will continue to expand in model coverage and in parameter space.
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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 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".