First direct measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi>Cu</mml:mi><mml:mprescripts/><mml:none/><mml:mn>59</mml:mn></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mi>p</mml:mi><mml:mo>,</mml:mo><mml:mi>α</mml:mi><mml:mo>)</mml:mo><mml:mmultiscripts><mml:mi>Ni</mml:mi><mml:mprescripts/><mml:none/><mml:mn>56</mml:mn></mml:mmultiscripts></mml:mrow></mml:math>: A step towards constraining the Ni-Cu cycle in the cosmos
Bibliographic record
Abstract
Reactions on proton-rich nuclides drive the nucleosynthesis in core collapse supernovae (CCSNe) and in x-ray bursts (XRBs). CCSNe eject the nucleosynthesis products to the interstellar medium and hence are a potential inventory of $p$ nuclei, whereas in XRBs nucleosynthesis powers the light curves. In both astrophysical sites the Ni-Cu cycle, which features a competition between $^{59}\mathrm{Cu}(p,\ensuremath{\alpha})^{56}\mathrm{Ni}$ and $^{59}\mathrm{Cu}(p,\ensuremath{\gamma})^{60}\mathrm{Zn}$, could potentially halt the production of heavier elements. Here, we report the first direct measurement of $^{59}\mathrm{Cu}(p,\ensuremath{\alpha})^{56}\mathrm{Ni}$ using a reaccelerated $^{59}\mathrm{Cu}$ beam and a cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of $^{56}\mathrm{Ni}$, and the experimental rate has been found to be lower than Hauser-Feshbach based statistical model predictions. New results hints that the $\ensuremath{\nu}p$ process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.
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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 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.020 | 0.015 |
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".