  We present a search for the production of a new heavy gauge boson W' that
decays to a top quark and a bottom quark. We have analyzed 230 pb^{-1} of data
collected with the Dzero detector at the Fermilab Tevatron collider at a
center-of-mass energy of 1.96 TeV. No significant excess of events above the
standard model expectation is found in any region of the final state invariant
mass distribution. We set upper limits on the production cross section of W'
bosons times branching ratio to top quarks at the 95% confidence level for
several different W' boson masses. We exclude masses between 200 GeV and 610
GeV for a W' boson with standard-model-like couplings, between 200 GeV and 630
GeV for a W' boson with right-handed couplings that is allowed to decay to both
leptons and quarks, and between 200 GeV and 670 GeV for a W' boson with
right-handed couplings that is only allowed to decay to quarks.
