Adjoint "quarks" on coarse anisotropic lattices: Implications for string breaking in full QCD

TL;DR

This study investigates string breaking in SU(2) gauge theory with adjoint quarks using coarse, anisotropic lattices and improved actions, providing insights into the static potential and gluelump states at large separations.

Contribution

It introduces a novel simulation approach with coarse anisotropic lattices and improved actions to efficiently study string breaking and related phenomena in SU(2) gauge theory.

Findings

Effective potentials at large separations were successfully measured.

Energy scales for string breaking were established via gluelump states.

Correlation functions support the relevance of Wilson loops for string breaking studies.

Abstract

A detailed study is made of four dimensional SU(2) gauge theory with static adjoint ``quarks'' in the context of string breaking. A tadpole-improved action is used to do simulations on lattices with coarse spatial spacings $a_s$, allowing the static potential to be probed at large separations at a dramatically reduced computational cost. Highly anisotropic lattices are used, with fine temporal spacings $a_t$, in order to assess the behavior of the time-dependent effective potentials. The lattice spacings are determined from the potentials for quarks in the fundamental representation. Simulations of the Wilson loop in the adjoint representation are done, and the energies of magnetic and electric ``gluelumps'' (adjoint quark-gluon bound states) are calculated, which set the energy scale for string breaking. Correlators of gauge-fixed static quark propagators, without a connecting string of spatial links, are analyzed. Correlation functions of gluelump pairs are also considered; similar correlators have recently been proposed for observing string breaking in full QCD and other models. A thorough discussion of the relevance of Wilson loops over other operators for studies of string breaking is presented, using the simulation results presented here to support a number of new arguments.