PROBING COLOR-SINGLET EXCHANGE IN Z-JET EVENTS AT THE CERN LHC(2)

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 o f phase-space region allows the suppression of QCD backgrounds to the level of the signal. The color-singlet-exchange signal can be distingu ished from QCD backgrounds by the radiation patterns of additional min ijets in individual events. A rapidity-gap trigger at the minijet leve l enhances substantially the signal versus the background. Analogous f eature of weak-boson scattering events make Z + 2-jet events at the CE RN LHC an ideal laboratory for investigation of the soft-jet activity expected in weak-boson scattering events.