arXiv subjects

Reinhard Alkofer

Publications and source records attributed to Reinhard Alkofer.

128 records · Page 8Linked to original sources

arXiv1995

Analytic Structure of the Quark Propagator in a Model with an infrared vanishing Gluon Propagator

The Dyson-Schwinger equation for the quark self energy is solved in rainbow approximation using an infrared (IR) vanishing gluon propagator that introduces an IR mass scale $b$. There exists a $b$ dependent critical coupling indicating the spontaneous breakdown of chiral symmetry. If one chooses realistic QCD coupling constants the strength and the scale of spontaneous chiral symmetry breaking decouple from the IR scale for small $b$ while for large $b$ no dynamical chiral symmetry breaking occurs. At timelike momenta the quark propagator possesses a pole, at least for a large range of the parameter $b$. Therefore it is suggestive that quarks are not confined in this model for all values of $b$. Furthermore, we argue that the quark propagator is analytic within the whole complex momentum plane except on the timelike axis. Hence the na\"ıve Wick rotation is allowed.

hep-ph↗

arXiv1993

Pion Loop Contribution to the Electromagnetic Pion Charge Radius

A phenomenological Dyson-Schwinger equation approach to QCD, formalised in terms of a QCD based model field theory, is used to calculate the electromagnetic charge radius of the pion. The contributions from the quark core and pion loop, as defined in this approach, are identified and compared. It is shown explicitly that the divergence of the charge radius in the chiral limit is due to the pion loop and that, at the physical value of the pion mass, this loop contributes less than 15\% to $\langle r^2_π\rangle$; i.e. the quark core is the dominant determining characteristic for the pion. This suggests that quark based models which fail to reproduce the $\ln\,m_π$ divergence of $\langle r^2_π\rangle$ may nevertheless incorporate the dominant characteristic of the pion: its quark core.

hep-ph↗