Study of lattice correlation functions at small times using the QCD sum rules continuum model

In this paper we study the work of Leinweber by applying the Continuum Model of QCD sum rules (QCDSR) to the analysis of (quenched) lattice correlation functions. We expand upon his work in several areas: we study meson states as well as baryons, we analyse data from several lattice spacings, and we include data from the Sheikholeslami-Wohlert (clover) improved action. We find that the QCDSR continuum model ansatz can reproduce the data, but only for nonphysical values of its parameters. This leads us to reject it as a model for hadronic correlation functions. We study the non-relativistic quark model and conclude that it predicts essentially the same form for the correlation function as the QCDSR continuum model approach. Furthermore, because it does not have the continuum model's restrictions on the parameters, the non-relativistic quark model can be viewed as a successful ansatz. As well as studying the validity or otherwise of the QCDSR continuum model approach, this paper defines 4-parameter fitting functions that can be used to fit lattice data even for a time window close to the source. These functions are shown to be an improvement over 2-exponential fits especially in the case of mesons. We encourage the application of this approach to situations where the conventional fitting procedures are problematic due to poor ground state dominance. (C) 1998 Elsevier Science B.V.