Observation of Diffractively Produced W and Z Bosons in pbar-p Collisions at root-s = 1800 GeV

Abstract

Using the D0 detector, we have observed events produced in pbar-p collisions that contain W or Z bosons in conjunction with very little energy deposition (``rapidity gaps'') in large forward regions of the detector. The fraction of W boson events with a rapidity gap (a signature for diffraction) is 0.89\pm^{0.19}_{0.17}%, and the probability that the non-diffractive background fluctuated to yield the observed diffractive signal is 3 x 10^{-14}, corresponding to a significance of 7.5 sigma. The Z boson sample has a gap fraction of 1.44 \pm^{0.61}_{0.52}%, with a significance of 4.4 sigma. The diffractive events have very similar properties to the more common non-diffractive component.