Static potential and local color fields in unquenched lattice QCD$_3$

TL;DR

This study demonstrates string breaking and the screening of the color-electric field in unquenched 3D lattice QCD with improved methods, providing clear evidence of quark vacuum polarization effects on confinement.

Contribution

It presents the first clear lattice QCD evidence of string breaking and flux-tube screening in unquenched three-dimensional QCD using an improved gluon action on coarse lattices.

Findings

Static potential saturates at twice the heavy-light meson mass.

Color-electric field strength tends to vacuum values at large quark separations.

Efficient simulation method enables exploration of large quark separations.

Abstract

String breaking by dynamical quarks in three-dimensional lattice QCD is analyzed through measurements of the potential and the local color-electric field strength generated by a static quark-antiquark pair. Simulations were done for unquenched SU(2) color with two flavors of staggered light quarks. An improved gluon action was used, which allows simulations to be done on coarse lattices, providing an extremely efficient means to access the large quark separations and long propagation times at which string breaking occurs. The static sources were generated using Wilson loop operators, hence no light valence quarks are present in the resulting trial states. Results give unambiguous evidence of string breaking. First the static potential is shown to saturate at twice the heavy-light meson mass at large separations. Then it is demonstrated that the local color-electric field strength in the region between the heavy quarks tends towards vacuum values at large separations, the first time that this most graphic effect of quark vacuum polarization on the confining flux-tube has been realized in lattice QCD. Implications of these results for unquenched simulations of four-dimensional QCD are drawn.