16 O (𝑒,𝑒′𝛼) 12 C measurements and the 12 C (𝛼,𝛾) 16 O astrophysical reaction rate
The 12 C (𝛼,𝛾) 16 O reaction, an important component of stellar helium burning, has a key role in nuclear astrophysics. It has significant impact on the evolution and final state of heavy to low mass stars, maximum mass of stellar formed black holes and also shapes the elemental abundances resulting from nucleosynthesis in such stars. Providing a reliable estimate for the energy dependence of this reaction at stellar helium burning temperatures has been a longstanding and important goal. In this work, we study the role of potential new 𝐸1 and 𝐸2 measurements of the 16 O (𝑒,𝑒′𝛼) 12 C reaction in reducing the overall uncertainty in the astrophysical 𝑆 factor for the 12 C (𝛼,𝛾) 16 O 𝐸1 and 𝐸2 ground state capture extrapolated to a stellar energy of 300 keV. A multilevel 𝑅-matrix analysis is used to make extrapolations of the 𝑆 𝐸1 (300 keV) and 𝑆 𝐸2 (300 keV) factors for the 12 C (𝛼,𝛾) 16 O reaction from existing ground state capture data. Bayesian analysis is used to quantify the uncertainties in the extrapolations for both the existing data alone and also when possible new experimental data are included. In particular, we consider a new experiment that would make use of a high-intensity low-energy electron beam that impinges on a windowless oxygen gas target as a means to determine the total 𝐸1 and 𝐸2 ground state cross sections for this reaction. Here we find that the new data could significantly reduce the 𝑆(300) uncertainties. Splitting the new data into high and low energy regions shows that both low and high energy data are effective in reducing the uncertainty.