  A search is presented for a singly produced excited bottom quark (b*)
decaying to a top quark and a W boson in the all-hadronic, lepton + jets, and
dilepton final states in proton-proton collisions at sqrt(s) = 8 TeV recorded
by the CMS experiment at the CERN LHC. Data corresponding to an integrated
luminosity of 19.7 inverse femtobarns are used. No significant excess of events
is observed with respect to standard model expectations. We set limits at 95%
confidence on the product of the b* quark production cross section and its
branching fraction to tW. The cross section limits are interpreted for
scenarios including left-handed, right-handed, and vector-like couplings of the
b* quark and are presented in the two-dimensional coupling plane based on the
production and decay coupling constants. The masses of the left-handed,
right-handed, and vector-like b* quark states are excluded at 95% confidence
below 1390, 1430, and 1530 GeV, respectively, for benchmark couplings. This
analysis gives the most stringent limits on the mass of the b* quark to date.
