Impact of O16(e,e′α)C12 measurements on the C12(α,γ)O16 astrophysical reaction rate

Abstract

The $^{12}$C($\\alpha,\\gamma$)$^{16}$O reaction, an important component of stellar helium burning, has a key role in nuclear astrophysics. It has direct impact on the evolution and final state of massive stars and also influences 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 measurements of the reaction, $^{16}$O($e,e \\alpha$)$^{12}$C reaction, in reducing the overall uncertainty. A multilevel $R$-matrix analysis is used to make extrapolations of the astrophysical S factor for the $^{12}$C($\\alpha,\\gamma$)$^{16}$O reaction to the stellar energy of 300 keV. The statistical precision of the $S$-factor extrapolation is determined by performing multiple fits to existing $E1$ and $E2$ ground state capture data, including the impact of possible future measurements of the $^{16}$O($e,e \\alpha$)$^{12}$C reaction. In particular, we consider a proposed MIT 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 $E2$ cross sections for this reaction.