Étude expérimentale de la réaction ³⁰Si(p,γ)³¹P pour comprendre les anomalies nucléosynthétiques dans les amas globulaires
Bibliographic record
Abstract
Globular clusters are essential objects for studying stellar evolution models and the early phases of galaxy formation. The abundance anomalies observed in the globular cluster NGC 2419, such as potassium overabundance and magnesium depletion, can be explained if an earlier generation of stars contaminates the currently observed stars. However, the nature and properties of this first generation of stars are not clearly identified. The temperature and density range of this one depends on a number of reaction rates. The ³⁰Si(p,γ)³¹P reaction is one of the few reactions identified as having sufficient influence to constrain the nature of the stellar site(s) that contaminated NGC 2419. The objective of this thesis is to reduce the nuclear uncertainties associated with the ³⁰Si(p,γ)³¹P reaction by determining the resonance strengths in the energy range of astrophysical interest. The study of this reaction was done via two distinct experiments. For low energy resonances, up to 500 keV above the threshold of proton emission, the ³⁰Si(³He,d)³¹P transfer reaction was performed at the Tandem of the MLL laboratory in Munich. The light particles produced during the reaction were momentum analyzed by the very high resolution Q3D magnetic spectrometer and their angular distributions were interpreted in the DWBA (Distorded Wave Born Approximation) framework to obtain the proton spectroscopic factors. These are essential for the calculation of the proton widths used to compute the strengths of the resonances. For higher energy resonances, a direct measurement of the resonance strengths was performed using the DRAGON recoil sperctrometer installed at TRIUMF in Vancouver, Canada. The results of these experiments were used to calculate the new rate of the ³⁰Si(p,γ)³¹P reaction and its astrophysical impact was studied in order to better constrain the stellar conditions that can explain the abundances observed in the stars of the globular cluster NGC 2419.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".