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Determination of the real part of the isospin-even forward scattering amplitude of low energy pion-nucleon scattering as a test of low energy quantumchromodynamics

Conference · · AIP Conf. Proc.; (United States)
OSTI ID:5960364
The real part of the isospin-even forward scattering amplitude Re D/sup +/ (t = 0) of the pion-nucleon scattering has been determined at an incident pion kinetic energy of 55 MeV by measuring the elastic scattering of positive and negative pions on protons within the Coulomb-nuclear interference region (t being the four momentum transfer). The value of Re D/sup +/ (t = 0) confirms the prediction of the Karlsruhe-Helsinki phase shift analysis/sup 1/ for that energy. These phases can be used to determine the sigma-term of pion-nucleon scattering by means of forward dispersion relations. Koch/sup 2/ obtained in such an analysis sigma = (64 +- 8) MeV at the Cheng-Dashen point t = 2 m/sup 2//sub ..pi../, ..nu.. = 0, which differs significantly from the value determined by chiral perturbation theory of QCD/sup 3/ sigma = (35 +- 5) MeV at t = ..nu.. = 0.
Research Organization:
Kernforschungszentrum Karlsruhe, Institut fuer Kernphysik und Universitaet Karlsruhe, Institut fuer Experimentelle Kernphysik, Postfach 3640, D 7500 Karlsruhe 1
OSTI ID:
5960364
Report Number(s):
CONF-860575-
Conference Information:
Journal Name: AIP Conf. Proc.; (United States) Journal Volume: 150:1
Country of Publication:
United States
Language:
English