  We investigate the prospect of the LHC for discovering new physics effects
via new strategies in the same-sign top pair and same-sign top pair associated
with a $W$ boson signatures. Significant enhancement in production of same-sign
top quarks (plus a $W$ boson) is a joint property of several models beyond the
standard model. We concentrate on the leptonic (electron and muon) decay of the
top quarks and study the exclusion reach of the LHC data for a simplified model
approach where top quark flavor changing could occur through a $Z'$ or a
neutral scalar $\phi$ exchange. Less background contributions and clean
signature are the advantages of the leptonic decay mode of the top quarks in
the same-sign production processes. A combination is performed on both
same-sign top pair and same-sign top pair plus a $W$ boson production modes
which enables us to reach a large fraction of the model parameter space.
Assuming the couplings of new physics of the order of $10^{-2}$, the mass of a
flavor changing $Z'$ or a neutral scalar above 1 TeV could be excluded. We
propose a momentum dependent charge asymmetry and angular observables in the
same-sign top process which provide the possibility of separation of new
physics signal from the SM backgrounds as well as discrimination of the flavor
changing $tuX$ from $tcX$, where $X = Z',\phi$.
