Monte Carlo uncertainty of the ³He(α,γ)7Be reaction rate.

Background: The ³He(α,γ)7Be reaction is of critical importance in determining the flux of solar neutrinos through the pp-II and pp-III chains. For this reason and others, the description of the cross section and its extrapolation towards low-energy has always been a matter of intense debate. While large systematic differences have been present in the past, several recent measurements are all in excellent statistical agreement. Purpose: The convergence of the recent individual experimental measurements of the ³He(α,γ)7Be reaction prompts a global analysis of the reaction data. From the combined data, a more precise estimate of the low-energy cross section can be determined. Results: A global R-matrix fit is used to describe the ³He(α,γ)7Be data as well as scattering data over a similar energy range. The R-matrix fit is then subjected to a Monte Carlo analysis to extract the uncertainties on the cross section and corresponding reaction rate. Conclusion: By combining several recent measurements of the ³He(α,γ)7Be reaction, the combined data yield a zero energy S factor of S(0) = 0.542 ± 0.011(MC fit) ± 0.006(model)-0.011+0.019 (phase shifts) keV b. This gives a total uncertainty in S(0) of +0.023/-0.017 keV b. [ABSTRACT FROM AUTHOR]