Probing color-singlet exchange in Z+2-jet events at the CERN LHC

The purely electroweak process qq --> qqZ (via t-channel gamma/Z or W exchange) provides a copious and fairly clean source of color-singlet exchange events in pp collisions at the CERN LHC. A judicious choice of phase-space region allows the suppression of QCD backgrounds to the level of the signal. The color-singlet-exchange signal can be distinguished from QCD backgrounds by the radiation patterns of additional minijets in individual events. A rapidity-gap trigger at the minijet level enhances substantially the signal versus the background. Analogous feature of weak-boson scattering events make Z + 2-jet events at the CERN LHC an ideal laboratory for investigation of the soft-jet activity expected in weak-boson scattering events.