  Searches for anomalous top quark-antiquark production are presented, based on
pp collisions at sqrt(s) = 8 TeV. The data, corresponding to an integrated
luminosity of 19.7 inverse femtobarns, were collected with the CMS detector at
the LHC. The observed ttbar invariant mass spectrum is found to be compatible
with the standard model prediction. Limits on the production cross section
times branching fraction probe, for the first time, a region of parameter space
for certain models of new physics not yet constrained by precision
measurements.
