Search for a Dark Photon and an Invisible Dark Higgs Boson in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>μ</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>μ</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math> and Missing Energy Final States with the Belle II Experiment
Bibliographic record
Abstract
The dark photon ${A}^{\ensuremath{'}}$ and the dark Higgs boson ${h}^{\ensuremath{'}}$ are hypothetical particles predicted in many dark sector models. We search for the simultaneous production of ${A}^{\ensuremath{'}}$ and ${h}^{\ensuremath{'}}$ in the dark Higgsstrahlung process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{A}^{\ensuremath{'}}{h}^{\ensuremath{'}}$ with ${A}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and ${h}^{\ensuremath{'}}$ invisible in electron-positron collisions at a center-of-mass energy of 10.58 GeV in data collected by the Belle II experiment in 2019. With an integrated luminosity of $8.34\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, we observe no evidence for signal. We obtain exclusion limits at 90% Bayesian credibility in the range of 1.7--5.0 fb on the cross section and in the range of $1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}--200\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ on the effective coupling ${ϵ}^{2}\ifmmode\times\else\texttimes\fi{}{\ensuremath{\alpha}}_{D}$ for the ${A}^{\ensuremath{'}}$ mass in the range of $4.0\text{ }\text{ }\mathrm{GeV}/{c}^{2}<{M}_{{A}^{\ensuremath{'}}}<9.7\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ and for the ${h}^{\ensuremath{'}}$ mass ${M}_{{h}^{\ensuremath{'}}}<{M}_{{A}^{\ensuremath{'}}}$, where $ϵ$ is the mixing strength between the standard model and the dark photon and ${\ensuremath{\alpha}}_{D}$ is the coupling of the dark photon to the dark Higgs boson. Our limits are the first in this mass range.
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.023 | 0.002 |
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".