NN potentials from IR chiral EFT

Chiral perturbation theory is nowadays a well-established approach to incorporate the chiral constraints from QCD. Nevertheless, for systems involving one baryon, the power counting which dictates the chiral order of observables is not as simple and consensual as in the purely mesonic case. The heavy baryon approach, which relies on a non-relativistic expansion around the limit of infinitely heavy baryon, recovers the usual power counting b ut destroys some analytic properties of the scattering amplitude. Some years ago, Becher and Leutwyler proposed a Lorentz-invariant formulation of chiral perturbation theory that maintains t he required analytic properties, but at the expense of a less intuitive power counting. Aware of the shortcomings of the heavy baryon formalism, the Sao Paulo group derived the twopion exchange component of the nucleon-nucleon potential in line with the works of Becher and Leutwyler. A striking result was that the long distance properties of the potential is determined by the specific low energy region of the pion-nucleon scatterin g amplitude where the heavy baryon expansion fails. In this talk I will discuss the origin of suc h failure and how it reflects in the asymptotics of the nucleon-nucleon interaction. Some results for phase shifts and deuteron properties will be shown, followed by a comparison with the heavy baryon predictions.