# Nuclear Physics Seminar: Dr. Mark Paris, Los Alamos National Laboratory

**Green function approach to R-matrix theory and applications to light nuclear reactions**

Dr. Mark Paris

Staff Member, Los Alamos National Laboratory

We analyze reactions of neutrons and charged-particles (p,d,t,h,a) on light elements (A < ~ 20). Our primary tool in this endeavor is the Green function of the Schroedinger equation, with boundary conditions prescribed at finite channel radii, in the phenomenological R-matrix approach. We review some elements of reaction theory in the R-matrix approach context and emphasize the multichannel unitarity of the formalism, which is essential to accurate phenomenological parametrization of the scattering and reaction observables. R-matrix parameters are related to various resonance-parameter representations and we discuss the analytic structure of the T-matrix amplitudes as a function of complex energy. Uncertainty quantification of the resulting observables is given. Several examples of R-matrix evaluations of light compound systems (NN, ^{5}Li, ^{7}Be, ^{10}Be, ^{17}O) are discussed briefly along with some plans for future work.

Hosted by Dr. deBoer

*All interested persons are invited to attend remotely—email physics@nd.edu for information.*

Originally published at physics.nd.edu.