Static and dynamic properties of the pion from continuum modelling of strong QCD

We present nonperturbative numerical solutions for the quark propagator Schwinger-Dyson equation (SDE) and pseudoscalar meson Bethe-Salpeter equation (BSE) at and beyond the rainbow-ladder truncation level of this system of equations. We solve this coupled system of integral equations using a phenomenological model for the dressed gluon propagator in Landau gauge as input. In the rainbow-ladder truncation scheme, we systematically calculate static properties of the pion and kaon. After combining the rainbow-ladder truncation for the SDE-BSE system with the impulse approximation for the pion-photon vertex, we present numerical results for the pion form factor using the Ball-Chiu and bare vertices for the nonperturbative quark-photon vertex. We find that the Ball-Chiu vertex satisfies electromagnetic current conservation automatically, however, this vertex gives a charge pion radius that is less than its experimental value, leaving room for further improvement. We go beyond the rainbow-ladder truncation by including pion cloud effects into the quark propagation, and then all the way up into the pion form factor. Here we find significant changes for the mass and decay constant of the pion. For the pion form factor, on the other hand, we find no qualitative changes in the Q² region studied for both vertices. Nevertheless, more work remains to be done at and beyond the rainbow-ladder truncation in order to connect the pion form factor to the model-independent perturbative result.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

Durham University

Year dc:date.issued

2010

Author dc:creator

• Cobos-Martinez, Jesus Javier