Insight into the Narrow Structure in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>η</mml:mi></mml:math>Photoproduction on the Neutron from Helicity-Dependent Cross Sections
Bibliographic record
Abstract
The double polarization observable $E$ and the helicity dependent cross sections ${\ensuremath{\sigma}}_{1/2}$ and ${\ensuremath{\sigma}}_{3/2}$ were measured for $\ensuremath{\eta}$ photoproduction from quasifree protons and neutrons. The circularly polarized tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost $4\ensuremath{\pi}$ detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from $\ensuremath{\eta}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ and $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}$. The results show that the narrow structure previously observed in $\ensuremath{\eta}$ photoproduction from the neutron is only apparent in ${\ensuremath{\sigma}}_{1/2}$ and hence, most likely related to a spin-$1/2$ amplitude. Nucleon resonances that contribute to this partial wave in $\ensuremath{\eta}$ production are only $N1/{2}^{\ensuremath{-}}$ (${S}_{11}$) and $N\text{ }1/{2}^{+}$ (${P}_{11}$). Furthermore, the extracted Legendre coefficients of the angular distributions for ${\ensuremath{\sigma}}_{1/2}$ are in good agreement with recent reaction model predictions assuming a narrow resonance in the ${P}_{11}$ wave as the origin of this structure.
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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".