  This Letter presents a search for tb resonances in 1.04/fb of LHC
proton-proton collision data collected by the ATLAS detector at a
center-of-mass energy of 7 TeV. Events with a lepton, missing transverse
momentum, and two jets are selected and the invariant mass of the corresponding
final state is reconstructed. The search exploits the shape of the tb invariant
mass distribution compared to the expected Standard Model backgrounds. The
model of a right-handed W'_R with Standard Model-like couplings is chosen as
the benchmark model for this search. No statistically significant excess of
events is observed in data, and upper limits on the cross section times the
branching ratio of W'_R resonances at 95% CL lie in the range 6.1-1.0 pb for
W'_R masses ranging from 0.5 to 2.0 TeV. These limits are translated into a
lower bound on the allowed right-handed W'_R mass, giving m_{W'_R} > 1.13 TeV
at 95% CL.
