Field strength correlators in full QCD

Abstract

We study, by numerical simulations on a lattice, the behaviour of the gauge-invariant two-point correlation functions of the gauge field strengths in the QCD vacuum with dynamical fermions.Comment: 11 pages, LaTeX file, + 2 PS figure

On the dependence of the gauge-invariant field-strength correlators in QCD on the shape of the Schwinger string

“…This means that the correlation length λ A defined in Refs. [17,18,19] is approximately path-independent, at least for the classes of paths that we have considered.…”

“…On the lattice we can define a lattice operator D (C)L µρ,νσ , which is proportional to D (C) µρ,νσ in the continuum limit, when the lattice spacing a → 0. Since the lattice analogue of the field strength is the open plaquette Π µρ (n) (the parallel transport along an elementary square of the lattice lying on the µρ-plane, starting from the lattice site n and coming back to n), D (C)L µρ,νσ will be defined as [17,18,19]…”

“…(1.1) and (1.2) is assumed to be the straight line connecting the points 0 and x. Lattice data [16,17,18,19], which are the input for these SVM calculations, also refer to the choice of the straight-line parallel transport. With this choice the Schwinger string (1.2) reads:…”

“…Then, in the Euclidean region, translational, O(4)-and parity invariance require the correlator (1.1) to be of the following form [4,5,6]: The functions D(x 2 ) and D 1 (x 2 ) have been directly determined by numerical simulations on a lattice in the quenched (i.e., pure-gauge) theory, with gauge group SU(2) [16], in the quenched SU(3) theory in the range of physical distances between 0.1 and 1 fm [17,18] and also in full QCD, i.e., including the effects of dynamical fermions [19].…”

Wilson-loop formalism for Reggeon exchange in soft high-energy scattering

“…Recalling from Eq. (4.47) that ζ ∼ 1/aE, and that the vacuum correlation length is of the order of a ∼ 0.2 ÷ 0.3 fm ∼ 1 ÷ 1.5 GeV −1 [64,65,66,67,68,69], we can estimate 49) which is less than one in the considered range of t and for not too heavy mesons. This estimate is quite conservative, and actually we expect that the typical transverse momentum of a parton involved in the process is of the same order of √ −t: for very small transferred momentum √ −t ≪ 1 GeV, we expect therefore that we can neglect the terms involving the transverse momentum of the partons, at least in a first approximation, so that the "contracted spin factors" are independent of ζ.…”