arXiv subjects
Publications and source records attributed to Enrico Meggiolaro.
We determine by numerical simulations on a lattice the gauge--invariant two--point correlation function of the gauge field strengths in the QCD vacuum, down to a distance of 0.1 fm.
In this paper we consider some analytic properties of the high--energy quark--quark scattering amplitude, which, as is well known, can be described by the expectation value of two lightlike Wilson lines, running along the classical trajectories of the two colliding particles. We shall prove that the expectation value of two infinite Wilson lines, forming a certain hyperbolic angle in Minkowski space--time, and the expectation value of two infinite Euclidean Wilson lines, forming a certain angle in Euclidean four--space, are connected by an analytic continuation in the angular variables. This could open the possibility of evaluating the high--energy scattering amplitude directly on the lattice or using the stochastic vacuum model. The Abelian case (QED) is also discussed.
In this paper we calculate the high--energy quark--quark scattering amplitude, first in the case of scalar QCD, using Fradkin's approach to derive the scalar quark propagator in an external gluon field and computing it in the eikonal approximation. (This approach was also recently used by Fabbrichesi, Pettorino, Veneziano and Vilkovisky to study the four--dimensional Planckian--energy scattering in gravity.) We then extend the results to the case of ``real'' ({\it i.e.} fermion) QCD, thus deriving again, in a rather direct way, the results previously found by Nachtmann. The abelian case (QED) is also discussed in the Appendix.