Nucleon axial and pseudoscalar form factors from the covariant Faddeev equation

Regular Article - Theoretical Physics

Abstract

We compute the axial and pseudoscalar form factors of the nucleon in the Dyson-Schwinger approach. To this end, we solve a covariant three-body Faddeev equation for the nucleon wave function and determine the matrix elements of the axialvector and pseudoscalar isotriplet currents. Our only input is a well-established and phenomenologically successful ansatz for the non-perturbative quark-gluon interaction. As a consequence of the axial Ward-Takahashi identity that is respected at the quark level, the Goldberger-Treiman relation is reproduced for all current-quark masses. We discuss the timelike pole structure of the quark-antiquark vertices that enters the nucleon matrix elements and determines the momentum dependence of the form factors. Our result for the axial charge underestimates the experimental value by 20 -25% which might be a signal of missing pion-cloud contributions. The axial and pseudoscalar form factors agree with phenomenological and lattice data in the momentum range above Q2 ~ 1...2 GeV2.

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Copyright information

© SIF, Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.Institut für Theoretische PhysikJustus-Liebig-Universität GiessenGiessenGermany

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