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Hrayr Matevosyan

Louisiana State University/JLab
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Quark-Gluon Vertex Dressing And Meson Masses
Beyond Ladder-Rainbow Truncation.

We include a generalized infinite class of quark-gluon vertex dressing
diagrams in a study of how dynamics beyond the ladder-rainbow truncation
influences the Bethe-Salpeter description of light quark pseudoscalar
and vector mesons. The diagrammatic specification of the vertex is
mapped into a corresponding specification of the Bethe-Salpeter kernel,
which preserves chiral symmetry.
This study adopts the algebraic format afforded by the simple
interaction kernel used in previous work on this topic. The new feature
of the present work is that in every diagram summed for the vertex and
the corresponding Bethe-Salpeter kernel, each quark-gluon vertex is
required to be the self-consistent vertex solution. We also adopt from
previous work the effective accounting for the role of the explicitly
non-Abelian three gluon coupling in a global manner through one
parameter determined from recent lattice-QCD data for the vertex. Within
the current model, the more consistent dressed vertex limits the
ladder-rainbow truncation error for vector mesons to be never more than
10% as the current quark mass is varied from the u/d region to the b
region.
We will also present our more recent results on fully dressing the
quark-gluon vertex function with only two point gluon lines. Once again,
we adopt the algebraic format afforded by the simple interaction kernel
for solving the quark GAP equation. The resulting quark propagator
functions exhibit large deviations from the corresponding Ladder-Rainbow
solutions.

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