  We address the issue of single top production in association with a W boson
at the Large Hadron Collider, in particular how to obtain an accurate
description in the face of the top pair production background given that the
two processes interfere with each other. We stress the advantages of an MC@NLO
description, and find that for cuts used to isolate the signal, it makes sense
to consider Wt as a well-defined production process in that the interference
with top pair production is small, and the cross-section of the former is above
the scale variation uncertainty associated with the latter. We also consider
the case where both Wt and top pair production are backgrounds to a third
process (Higgs boson production followed by decay to a W boson pair), and find
in this context that interference issues can also be neglected. We discuss the
generalization of our results to other situations, aided by a comparison
between the MC@NLO approach and a calculation of the WWbb final state matched
to a parton shower.
