R-matrix and K-matrix analysis of elastic alpha-alpha scattering

The R- and K-matrix parametrizations are analyzed and compared for the elastic alpha-alpha scattering at center-of-mass energies below 40 MeV. The two parametrizations differ in their definitions of the resonance energy which can lead to quite different results. The physical values of the best-fit parameters are compared with those computed for a potential model. The existence of a broad resonance near 9 MeV is not supported by the data or by the potential model. We discuss the positive and negative aspects for both parametrizations.