https://doi.org/10.1140/epja/i2008-10646-x
Regular Article - Theoretical Physics
UA(1) anomaly and 
-mass from an infrared singular quark-gluon vertex
1
Graz University, Universitätsplatz 5, A-8010, Graz, Austria
2
Institut für Kernphysik, TU Darmstadt, Schlossgartenstrasse 9, 64289, Darmstadt, Germany
3
Gesellschaft für Schwerionenforschung mbH, Planckstr. 1, D-64291, Darmstadt, Germany
* e-mail: richard.williams@physik.tu-darmstadt.de
Received:
24
April
2008
Accepted:
4
September
2008
Published online:
30
September
2008
The U
A(1) problem of QCD is inevitably tied to the infrared behaviour of quarks and gluons with its most visible effect being the -mass. A dimensional argument of Kogut and Susskind showed that the mixing of the pseudoscalar flavour-singlet mesons with gluons can provide a screening of the Goldstone pole in this channel if the full quark-quark interaction is strongly infrared singular as ∼ 1/k
4 . We investigate this idea using previously obtained results for the Landau gauge ghost and gluon propagator, together with recent determinations for the singular behaviour of the quark-gluon vertex. We find that, even with an infrared vanishing gluon propagator, the singular structure of the quark-gluon vertex for certain kinematics is apposite for yielding a non-zero screening mass.
PACS: 11.30.Rd Chiral symmetries – / 11.30.Fs Global symmetries (e.g., baryon number, lepton number) – / 12.38.Lg Other nonperturbative calculations – / 14.40.Aq 
, K , and 
mesons –
© SIF, Springer-Verlag Berlin Heidelberg, 2008
