Monopole-antimonopole correlation functions in 4D U(1) gauge theory

We study the two-point correlator of a modified Confined-Coulomb transition order parameter in four dimensional compact U(1) lattice gauge theory with Wilson action. Its long distance behavior in the confined phase turns out to be governed by a single particle decay. The mass of this particle is computed and found to be in agreement with previous calculations of the 0^{++} gaugeball mass. Remarkably, our order parameter allows to extract a good signal to noise ratio for masses with low statistics. The results we present provide a numerical check of a theorem about the structure of the Hilbert space describing the confined phase of four dimensional compact U(1) lattice gauge theories.