R-matrix analysis of interference effects in C-12(alpha,alpha)C-12 and C-12(alpha,gamma)O-16 - art. no. 064611

The alpha+C-12 d phase shift and the C-12(alpha,gamma)O-16 E2 S factor are analyzed in the R-matrix theory. A new method is proposed to link experimen tal and calculated parameters within the R-matrix formalism. We show that i nterference patterns in the phase shift near 3 MeV are very helpful to cons train the parameter set. Starting from this analysis, we fit the C-12(alpha ,gamma)O-16 E2 S factor, and find low-energy values larger than currently a ccepted. Different interference patterns are found, but do not appear to af fect the astrophysical energies. Consequently, direct measurements at low e nergies are necessary for astrophysical applications.