Residues of the S-matrix for several [formula omitted] resonances from the Jost function analysis

Abstract

Parameters of the O16 resonances 0+, 1−, 2+, 3−, and 4+ as well as the corresponding residues of the S-matrix are extracted from experimental data on elastic α12C scattering. This is done by locating zeros of the Jost function at complex energies. The Jost function is constructed by fitting the corresponding partial cross sections for the elastic α12C-scattering. These cross sections are obtained from the available R-matrix analysis of the raw experimental data. An exact semi-analytic representation for the Jost function is used, where all the factors responsible for the branching of the Riemann surface are given explicitly. The remaining unknown functions in this representation are approximated by several terms of the Taylor series where the expansion coefficients serve as the data-fitting parameters. Such an approximation does not affect the correct analytic structure of the Jost function, and thus the corresponding analytic structure of the S-matrix also remains correct.