An electron fixed target experiment to search for a new vector boson A′ decaying to e+e−
Bibliographic record
Abstract
We describe an experiment to search for a new vector boson A′ with weak coupling α′ ≳ 6 × 10−8 α to electrons (α = e 2/4π) in the mass range 65 MeV < m A′ < 550 MeV. New vector bosons with such small couplings arise naturally from a small kinetic mixing of the “dark photon” A′ with the photon — one of the very few ways in which new forces can couple to the Standard Model — and have received considerable attention as an explanation of various dark matter related anomalies. A′ bosons are produced by radiation off an electron beam, and could appear as narrow resonances with small production cross-section in the trident e + e − spectrum. We summarize the experimental approach described in a proposal submitted to Jefferson Laboratory’s PAC35, PR-10-009 [1]. This experiment, the A′ Experiment (APEX), uses the electron beam of the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory (CEBAF) at energies of ≈ 1–4 GeV incident on 0:5 − 10% radiation length Tungsten multi-foil targets, and measures the resulting e + e − pairs to search for the A′ using the High Resolution Spectrometer and the septum magnet in Hall A. With a ∼ 1 month run, APEX will achieve very good sensitivity because the statistics of e + e − pairs will be ∼ 10,000 times larger in the explored mass range than any previous search for the A′ boson. These statistics and the excellent mass resolution of the spectrometers allow sensitivity to α′/α one to three orders of magnitude below current limits, in a region of parameter space of great theoretical and phenomenological interest. Similar experiments could also be performed at other facilities, such as the Mainz Microtron.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".