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Parameterization of Direct and Doorway Processes in R-Matrix Formalism

Publication Type
Conference Paper
Book Title
15th International Conference on Nuclear Data for Science and Technology (ND2022)
Publication Date
Page Number
Publisher Location
United States of America
Conference Name
15th International Conference on Nuclear Data for Science and Technology (ND2022)
Conference Location
Livermore (VIRTUAL), California, United States of America
Conference Sponsor
Lawrence Livermore National Laboratory
Conference Date

R-matrix formalism is extended beyond compound nuclear (CN) resonant reactions to include parameterization of direct as well as doorway processes. Direct processes in the R-matrix exterior are parameterized by a unitary matrix that introduces mixing among wave function coefficients of the incoming and outgoing wave function components at the R-matrix channel surface. Doorway processes are parameterized by separating the Hilbert space of the interior R-matrix region into its doorway and CN subspaces, from which doorway state eigenenergies, reduced width amplitudes, and the strengths of their coupling to CN levels appear as new R-matrix parameters. Parameterization of generalized as well as the conventional Reich–Moore approximation for eliminated capture channels in the presence of direct, doorway, and CN processes is presented along with a complex-valued scattering length with contributions from direct, doorway, and CN capture processes. Derivation of Brune’s alternative R-matrix parameters is extended to include doorway states. This work suggests how R-matrix formalism could be extended further by adopting the concepts from related reaction formalisms.