Zero temperature string breaking in lattice quantum chromodynamics

TL;DR

This paper confirms the occurrence of string breaking in lattice QCD at zero temperature by analyzing the mixing between the string state and two-meson states, providing clear evidence despite weak mixing signals.

Contribution

It provides the first clear lattice QCD evidence of string breaking at zero temperature by studying mixing effects with dynamical quarks.

Findings

Weak mixing between string and two-meson states

Mixing decreases at level crossing

Confirmation of string breaking in lattice QCD

Abstract

The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or "string", which should break in the presence of light quark-antiquark pairs. This expected zero-temperature phenomenon has proven elusive in simulations of lattice QCD. We study mixing between the string state and the two-meson decay channel in QCD with two flavors of dynamical sea quarks. We confirm that mixing is weak and find that it decreases at level crossing. While our study does not show direct effects of internal quark loops, our results, combined with unitarity, give clear confirmation of string breaking.