Jesse Brown

This technical memorandum compiles the contributions presented at the 2026 R-Matrix Workshop on Methods and Applications, held July 13–17, 2026, at Oak Ridge National Laboratory. The workshop brought together researchers working in phenomenological R-matrix theory, experimental nuclear physics, nuclear-data evaluation, uncertainty quantification, and computational methods, with particular emphasis on neutron-induced reactions. The collected contributions cover foundational R-matrix theory and experimental techniques; resolved- and unresolved-resonance-region analyses; automated resonance fitting and uncertainty quantification; statistical and parametric approaches to nuclear-data evaluation; and relativistic, multistep, and distant-pole formulations. Applications to specific compound-nuclear systems, charged-particle reactions, thermal scattering, neutron transmission, and nuclear-data validation are also presented. The memorandum documents recent developments in widely used analysis and processing tools, including EDA, AZURE2, SAMMY, AMPX, and SCALE, together with emerging Python-based implementations and new optimization methods. Additional contributions describe experimental capabilities and measurements at facilities including the Los Alamos Neutron Science Center and the Spallation Neutron Source, including the VENUS neutron time-of-flight instrument. Collectively, these contributions provide a representative account of current R-matrix methods, practical evaluation challenges, and emerging research directions. This memorandum is intended to preserve the technical content of the workshop and to serve as a reference for experimentalists, theorists, nuclear-data evaluators, software developers, students, and users of evaluated nuclear data in applications ranging from nuclear astrophysics to criticality safety.

The U.S. Department of Energy's Office of Scientific and Technical Information