First measurement of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">S</mml:mi><mml:mprescripts/><mml:none/><mml:mn>30</mml:mn></mml:mmultiscripts><mml:mo>+</mml:mo><mml:mi>α</mml:mi></mml:mrow></mml:math> resonant elastic scattering for the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mmultiscripts><mml:mi mathvariant="normal">S</mml:mi><mml:mprescripts/><mml:none/><mml:mn>30</mml:mn></mml:mmultiscripts><mml:mo>(</mml:mo><mml:mi>α</mml:mi><mml:mo>,</mml:mo><mml:mi>p</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math> reaction rate
Bibliographic record
Abstract
Background: Type I x-ray bursts are the most frequently observed thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of an accreting neutron star. The $^{30}\mathrm{S}(\ensuremath{\alpha},p)$ reaction plays a critical role in burst models, yet insufficient experimental information is available to calculate a reliable, precise rate for this reaction.Purpose: Our measurement was conducted to search for states in $^{34}\mathrm{Ar}$ and determine their quantum properties. In particular, natural-parity states with large $\ensuremath{\alpha}$-decay partial widths should dominate the stellar reaction rate.Method: We performed the first measurement of $^{30}\mathrm{S}+\ensuremath{\alpha}$ resonant elastic scattering up to a center-of-mass energy of 5.5 MeV using a radioactive ion beam. The experiment utilized a thick gaseous active target system and silicon detector array in inverse kinematics.Results: We obtained an excitation function for $^{30}\mathrm{S}(\ensuremath{\alpha},\ensuremath{\alpha})$ near ${150}^{\ensuremath{\circ}}$ in the center-of-mass frame. The experimental data were analyzed with $R$-matrix calculations, and we observed three new resonant patterns between 11.1 and 12.1 MeV, extracting their properties of resonance energy, widths, spin, and parity.Conclusions: We calculated the resonant thermonuclear reaction rate of $^{30}\mathrm{S}(\ensuremath{\alpha},p)$ based on all available experimental data of $^{34}\mathrm{Ar}$ and found an upper limit about one order of magnitude larger than a rate determined using a statistical model. The astrophysical impact of these two rates has been investigated through one-zone postprocessing type I x-ray burst calculations. We find that our new upper limit for the $^{30}\mathrm{S}(\ensuremath{\alpha},p)^{33}\mathrm{Cl}$ rate significantly affects the predicted nuclear energy generation rate during the burst.
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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 | 0.008 | 0.005 |
| Meta-epidemiology (narrow) | 0.005 | 0.008 |
| Meta-epidemiology (broad) | 0.002 | 0.009 |
| Bibliometrics | 0.002 | 0.004 |
| Science and technology studies | 0.009 | 0.007 |
| Scholarly communication | 0.006 | 0.007 |
| Open science | 0.009 | 0.008 |
| Research integrity | 0.006 | 0.008 |
| Insufficient payload (model declined to judge) | 0.151 | 0.010 |
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; both teacher heads agree on what is shown here.
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".