Chatrchyan, S (reprint author), Yerevan Phys Inst, Yerevan 375036, Armenia.
Searches for anomalous top quark-antiquark production are presented, based on pp collisions at root s = 8 TeV. The data, corresponding to an integrated luminosity of 19.7 fb(-1), were collected with the CMS detector at the LHC. The observed t (t) over bar 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.