Determination of the real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering at 55 MeV as a test of low-energy quantum chromodynamics

U. Wiedner; K. Göring; J. Jaki; U. Klein; W. Kluge; H. Matthäy; M. Metzler; E. Pedroni; W. Fetscher; H. J. Gerber; R. Koch

doi:10.1103/PhysRevLett.58.648

Determination of the real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering at 55 MeV as a test of low-energy quantum chromodynamics

U. Wiedner, K. Göring, J. Jaki, U. Klein, W. Kluge, H. Matthäy, M. Metzler, E. Pedroni, W. Fetscher, H. J. Gerber, and R. Koch

Phys. Rev. Lett. 58, 648 – Published 16 February 1987

Abstract

The real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering has been determined at a pion energy of $T_{π}$ =55 MeV by measurement of the elastic scattering of positive and negative pions on protons within the Coulomb-nuclear interference region. The value confirms the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. These phases have been used to determine the σ term of pion-nucleon scattering by means of dispersion relations, resulting in a value for σ which is in contradiction with chiral perturbation theory of QCD.

Received 25 September 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.648

Authors & Affiliations

U. Wiedner, K. Göring, J. Jaki, U. Klein, W. Kluge, H. Matthäy, and M. Metzler

Institut für Kernphysik, Kernforschungszentrum Karlsruhe, Karlsruhe, Federal Republic of Germany and Institut für Experimentelle Kernphysik, Universitat Karlsruhe, D-7500 Karlsruhe 1, Federal Republic of Germany

E. Pedroni