  We present a search for hypothetical vector-like quarks in ppbar collisions
at sqrt(s) = 1.96 TeV. The data were collected by the D0 detector at the
Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4
fb^(-1). We select events with a final state composed of a W or Z boson and a
jet consistent with a heavy object decay. We observe no significant excess in
comparison to the background prediction and set limits on production cross
sections for vector-like quarks decaying to W+jet and Z+jet. These are the most
stringent mass limits for electroweak single vector-like quark production at
hadron colliders.
