Münster 2011 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 42: Hadronenstruktur und -spektroskopie VII
HK 42.1: Group Report
Wednesday, March 23, 2011, 16:30–17:00, C-2
Photon- and pion-nucleon interactions in a unitary and causal effective field theory based on the chiral Lagrangian — •Ashot Gasparyan1,2 and Matthias Lutz1 — 1GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstrasse 1, 64291 Darmstadt, Germany — 2SSC RF ITEP, Bolshaya Cheremushkinskaya 25, 117218 Moscow, Russia
We present and apply a novel scheme for studying photon- and pion-nucleon scattering beyond the threshold region [1]. Partial-wave amplitudes for the γ N and π N states are obtained by an analytic extrapolation of subthreshold reaction amplitudes computed in chiral perturbation theory, where the constraints set by electromagnetic-gauge invariance, causality and unitarity are used to stabilize the extrapolation. Based on the chiral Lagrangian we recover the empirical s- and p-wave amplitudes up to energies √s≃ 1300 MeV in terms of the parameters relevant at order Q3.
[1] A. Gasparyan, M. F. M. Lutz, Nucl. Phys. A848, 126-182 (2010). [arXiv:1003.3426 [hep-ph]].