The renormalization of EFT for nucleon-nucleon scattering in nonperturbative regimes is investigated in a compact parametrization of the T -matrix. The key difference between perturbative and nonperturbative renormalization is clarified. The underlying theory perspective and the ’fixing’ of the prescriptions for the T -matrix from physical boundary conditions are stressed.

In a recent Letter [1], Kondo and Morimatsu present a QCD sum rule calculation of nucleon-nucleon scattering lengths. They also relate the empirical scattering lengths to the nucleon mass shift δM in nuclear matter to cast doubt on the " linear density approximation. " In this Comment, we point out flaws in both parts of their analysis. It is useful to start with the (nonrelativistic) optical p...

We perform a nonperturbative calculation of the S0 NN scattering amplitude, using an effective field theory (EFT) expansion. We use dimensional regularization throughout, and the MS renormalization scheme; our final result depends only on physical observables. We show that the EFT expansion of the quantity |p| cot δ(p) converges at momenta much greater than the scale Λ that characterizes the de...

The discrete energy-eigenvalues of two nucleons interacting with a finite-range nuclear force and confined to a harmonic potential are used to numerically reconstruct the free-space scattering phase shifts. The extracted phase shifts are compared to those obtained from the exact continuum scattering solution and agree within the uncertainties of the calculations. Our results suggest that it mig...

The sensitivity of nucleon-nucleus elastic scattering observables to the offshell structure of nucleon-nucleon t-matrices, derived from realistic NN potentials, is investigated within the context of a full-folding model based on the impulse approximation. Our study uses recently developed NN potential models, which describe a subset of the NN data base with a χ2 per datum ∼1, which means that t...

Virtual Compton Scattering off the proton: γ∗p → γp is a new field of investigation of nucleon structure. Several dedicated experiments have been performed at low c.m. energy and various momentum transfers, yielding specific information on the proton. This talk reviews the concept of nucleon Generalized Polarizabilities and the present experimental status. Virtual Compton Scattering (VCS) off t...