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. 
J. Humblet (Caltech, Kellogg Lab.), A. Csoto (Los Alamos), K. Langanke   (Aarhus University)