Measurement of the proton’s G[sub Ep]/G[sub Mp] ratio to Q[sup 2]=5.6 GeV[sup 2] at JLab
Bibliographic record
Abstract
The ratio of the electric and magnetic proton form factors, GEp/GMp, has been studied in the Thomas Jefferson National Accelerator Facility (Hall) A at JLab in two experiments, from measurements of the longitudinal and transverse polarization of the recoil proton, Pl and Pt, respectively, in the elastic scattering of polarized electrons, e⃗p→ep⃗. Together, these experiments cover the Q2-range 0.5 to 5.6 GeV2. The results of the second experiment are discussed here; although preliminary, they confirm and extend the finding of the first experiment, that the ratio μpGEp/GMp, which is close to 1 for Q2<0.8 GeV2, decreases approximately linearly with Q2 above this momentum transfer squared, and reaches a value ∼0.19 at Q2=5.6 GeV2. The new results presented here have been obtained by measuring the recoil proton polarization in e⃗p→ep⃗, which provides a better way to obtain GEp, even in the presence of a dominant magnetic form factor. Precision measurements of polarization observables have become possible with the advent of polarized electron beams with ≈100% duty factor, high current and high polarization.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".