On the sensitivity of extracting the astrophysical cross section factor of the 12C(a,g) reaction from existing data [Comment on Schuermann et al. Phys. Lett. B711(2012)35]

TL;DR

This paper critically examines the extraction of the astrophysical cross section factor for the 12C(a,g) reaction, highlighting significant uncertainties and questioning recent claims of high precision in existing data analysis.

Contribution

It demonstrates that previous claims of 12% accuracy rely on data with large errors, and clarifies the ambiguities in the S_E1 and S_E2 values at low energies.

Findings

Large error bars in data invalidate 12% accuracy claim.

Significant deviations in S_E2 values challenge previous extrapolations.

Current data still contain ambiguities in key astrophysical parameters.

Abstract

We address a conflicting report on the value and uncertainty of the astrophysical cross section factor of the 12C(a,g) reaction extracted from existing data. In sharp contrast to previously reported ambiguities (by up to a factor 8), Schuermann et al. suggest an accuracy of 12%. We demonstrate that the so claimed "rigorous data selection criteria" used by Schuermann et al. relies on the s-factors extracted by Assuncao et al. But these results were shown in a later analysis (by this author) to have large error bars (considerably larger than claimed by Assuncao em et al.) which render these data not appropriate for a rigorous analysis. When their "rigorous data selection" is adjusted to remove the results of Assuncao et al. the astrophysical cross section factor cannot be extracted with 12% accuracy, or even close to it. Such data on the S_E2 values at low energies deviate by up to a factor two from their fit and exhibit a sharper slope rising toward low energies, leading to strong doubt on their extrapolated S_E2(300) value and the quoted small error bar. Contrary to their claim the small value of S_E1(300) ~10 keVb cannot be ruled out by current data including the most modern gamma-ray data. As previously observed by several authors current data reveal ambiguities in the value of S_E1(300) ~10 keVb or ~80 keVb, and the new ambiguity that was recently revealed (by this author) of S_E2(300) ~60 keVb or ~154 keVb, appear to be a more reasonable evaluation the status of current data.