A potential between heavy-light mesons is extracted from quark correlation functions in the framework of quenched lattice QCD with Kogut-Susskind fermions. We show that the resulting potential is attractive at short distances. An analysis of the influence of the light quark mass on the interaction is performed.
We investigate the eigenvalue spectrum of the staggered Dirac matrix in SU(3) gauge theory and in full QCD on a 6 3 × 4 lattice. As a measure of the fluctuation properties of the eigenvalues, we study the nearest-neighbor spacing distribution P (s) for various values of β both in the confinement and in the deconfinement phase. In both phases except far into the deconfinement region, the lattice data agree with the Wigner surmise of random-matrix theory which is indicative of quantum chaos. We do not find signs of a transition to Poisson regularity at the deconfinement phase transition.
An effective residual interaction for a meson-meson system is computed in lattice QCD. We describe the theoretical framework and present its application to the I = 2 channel S-wave interaction of the π-π system. Scattering phase shifts are also computed and compared to experimental results.
The interaction of spatially extended heavy baryons is investigated in the framework of lattice QCD with dynamical quarks. It is shown that the expected dipole forces have a very short range and that the baryon-antibaryon interaction is more attractive than the baryon-baryon interaction. Sea quarks play a minor important role. 1 Supported in part by "Fonds zur F orderung der wissenschaftlichen Forschung" under Contract No. P7510-TEC. 1 1. Introduction. Quark theory provides new degrees of freedom at the subnuclear level which were previously considered by meson theory. The vacuum of QCD contains both virtual gluons and quarks. As a consequence the nucleon-nucleon forces are mediated for short distances by gluon exchange between the constituent quarks whereas for longer distances the production of quark-antiquark pairs is the dominating mechanism. The quark-antiquark exchange can be treated as an e ective meson exchange leading to the construction of the Bonn and Paris potentials 1]. The meson theoretical potentials give a satisfactory description of the nucleon-nucleon scattering data which are mainly sensitive to long range distances. The gluon exchange can be studied by phenomenological potential and bag models allowing for a rst insight into the interaction mechanism of the six-quark system 2].Both quark and meson potentials contain parameters and are based on phenomenology. Today the aim should be to calculate the nucleon-nucleon forces directly from the eld equations of QCD. Although we are at present far from a treatment of complete QCD from rst principles some attempts can be performed in the framework of a restricted QCD. In the last decade the simulation of quantum eld theories on computers made fast progress and reached a high standard. Thus, one should start now with the investigation of nucleon-nucleon interactions on the basis of a truncated (and maybe unrealistic) QCD. One restriction is to neglect quark loops in the action and to take only gluon exchange into account. Another approximation is to reduce the dynamical propagators of the valence quarks of the hadron to static propagators. This can be weakened by making one propagator dynamical and leaving the others as spectator quarks. With the development of the next computer generations the codes can be extended step by step in order to take nally the full QCD process into account. During the last years lattice calculations have demonstrated that the potential between a static quark and a static antiquark of a meson is con ning. The same result turns out for the three quarks of a baryon 3]. All these outcomes of the static approximation make us believe QCD to be the proper theory of strong interactions. Thus, an application of
A method for the extraction of an e ective meson-meson potential from Green functions, which can be obtained from a lattice simulation, is presented. Simulations are carried out for compact QED and QCD in four dimensions using the quenched approximation and the hopping parameter expansion. In a further study, a heavy-light meson is considered employing a conjugate gradient algorithm for the light propagators. Due to the Pauli exclusion principle, the results for QED indicate the existence of a hard core, but for QCD there is strong attraction at small meson distances.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.