Abstract
An important class of interference terms is included in the ABFST multiperipheral model by adding an extra term to the inhomogeneous term and to the kernel of the integral equation. This additional term corresponds to the contribution to the 2-to-4 cross section from interchanging one or two pairs of particles from two different vertices. It is found that these interference terms change only slightly the position of the output vacuum pole, although they give a non-negligible contribution to the four-particle production cross section.