Eur. Phys. J. A (2004) 19: 401-412
https://doi.org/10.1140/epja/i2003-10129-8

Improving the convergence of the chiral expansion for nuclear forces - II: Low phases and the deuteron

¹ Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44870, Bochum, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik (Theorie), Universität Bonn, Nußallee 14-16, D-53115, Bonn, Germany
³ Jefferson Laboratory, VA 23606, Newport News, USA

^* e-mail: evgeni.epelbaum@tp2.ruhr-uni-bochum.de

Abstract

Recently, we have proposed a new cut-off scheme for pion loop integrals in the two-pion exchange potential. This method allows for a consistent implementation of constraints from pion-nucleon scattering and has been successfully applied to peripheral nucleon-nucleon partial waves. We now consider low partial waves in the non-perturbative regime, where the regularized Lippmann-Schwinger equation has to be solved in order to generate the bound and scattering states. We observe an improved description of most of the phase shifts when going from next-to- to next-to-next-to-leading order in the chiral expansion. We also find a good description of the deuteron properties. In addition, the new cut-off scheme allows to avoid the presence of unphysical deeply bound states. We discuss the cut-off dependence of the four-nucleon low-energy constants and show that their numerical values can be understood in terms of resonance saturation. This connects the effective field theory approach to boson exchange phenomenology.