String breaking as a mixing phenomenon in the SU(2) Higgs model

We study the fundamental potential in the confinement "phase" of the SU(2) Higgs model. Around separation r(b), the confining string of the gauge field breaks by formation of a dynamical pair of light quarks. The ground state and first excited state static potentials are determined by a variational technique from a matrix correlation in which suitably smeared gauge and Higgs fields enter. Our results at beta = 2.4 clearly show string breaking (r(b) approximate to 1.9r(0)). The investigation of properly defined overlaps confirms the interpretation of string breaking as a level crossing phenomenon between string-type and meson-type states. We study the scaling properties of the static potentials along a line of constant physics, varying the lattice spacing by a factor of 2. Our results show compatibility with scaling within tiny errors. (C) 2000 Elsevier Science B.V. All rights reserved.