Normal single-spin asymmetries in electron-proton scattering: Two-photon exchange with intermediate-state resonances
Bibliographic record
Abstract
We calculate the beam (${B}_{n}$) and target (${A}_{n}$) normal single-spin asymmetries in electron--proton elastic scattering from two-photon exchange amplitudes with resonance intermediate states of spin-parity $1/{2}^{\ifmmode\pm\else\textpm\fi{}}$ and $3/{2}^{\ifmmode\pm\else\textpm\fi{}}$ and mass $W\ensuremath{\lesssim}1.8$ GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton to the excited resonance states. For ${B}_{n}$, the spin 3/2 resonances dominate by an order of magnitude over the spin 1/2 states. In general we observe cancellations between the negative contributions of the $\mathrm{\ensuremath{\Delta}}(1232)$ and $N(1520)$ across both beam energy and scattering angle, and the positive contributions of the $\mathrm{\ensuremath{\Delta}}(1700)$ and $N(1720)$, leading to a rather large overall uncertainty band in the total ${B}_{n}$. At forward angles and beam energies ${E}_{\text{lab}}<1$ GeV, where the $\mathrm{\ensuremath{\Delta}}(1232)$ dominates, the calculated ${B}_{n}$ tend to overshoot the A4 and SAMPLE data. The calculated ${B}_{n}$ compare well with the measured values from the A4 and ${Q}_{\text{weak}}$ experiments with ${E}_{\text{lab}}>1$ GeV.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".