  Results are presented from a search for the production of a heavy gauge boson
W' decaying into a top and a bottom quark, using a data set collected by the
CMS experiment at sqrt(s) = 8 TeV and corresponding to an integrated luminosity
of 19.5 inverse femtobarns. Various models of W'-boson production are studied
by allowing for an arbitrary combination of left- and right-handed couplings.
The analysis is based on the detection of events with a lepton (e, mu), jets,
and missing transverse energy in the final state. No evidence for W'-boson
production is found and 95% confidence level upper limits on the production
cross section times branching fraction are obtained. For W' bosons with purely
right-handed couplings, and for those with left-handed couplings assuming no
interference effects, the observed 95% confidence level limit is M(W') > 2.05
TeV. For W' bosons with purely left-handed couplings, including interference
effects, the observed 95% confidence level limit is M(W') > 1.84 TeV. The
results presented in this paper are the most stringent limits published to
date.
