First measurement of coherent <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>ϕ</mml:mi></mml:math>-meson photoproduction from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>He</mml:mi><mml:mprescripts/><mml:none/><mml:mn>4</mml:mn></mml:mmultiscripts></mml:math> near threshold
Bibliographic record
Abstract
The differential cross sections and decay angular distributions for coherent $\ensuremath{\phi}$-meson photoproduction from helium-4 are measured for the first time at forward angles with linearly polarized photons in the energy range ${E}_{\ensuremath{\gamma}}=1.685--2.385\phantom{\rule{4.pt}{0ex}}\text{GeV}$. Thanks to the target with spin-parity ${J}^{P}={0}^{+}$, unnatural-parity exchanges are absent, and thus natural-parity exchanges can be investigated clearly. The decay asymmetry with respect to photon polarization is shown to be very close to the maximal value. This ensures the strong dominance ($>94$%) of natural-parity exchanges in this reaction. To evaluate the contribution from natural-parity exchanges to the forward cross section ($\ensuremath{\theta}={0}^{\ensuremath{\circ}}$) for the $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\phi}p$ reaction near threshold, the energy dependence of the forward cross section ($\ensuremath{\theta}={0}^{\ensuremath{\circ}}$) for the $\ensuremath{\gamma}^{4}\mathrm{He}\ensuremath{\rightarrow}\ensuremath{\phi}^{4}\mathrm{He}$ reaction is analyzed. The comparison to $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\phi}p$ data suggests that enhancement of the forward cross section arising from natural-parity exchanges and/or destructive interference between natural-parity and unnatural-parity exchanges is needed in the $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\phi}p$ reaction near threshold.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| 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) | 0.009 | 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".