  The CDF collaboration has recently reported a large deviation from the
standard model of the t \bar t forward-backward asymmetry in the high invariant
mass region. We interpret this measurement as coming from new physics at a
heavy scale Lambda, and perform a model-independent analysis up to
O(1/Lambda^4). A simple formalism to test and constrain models of new physics
is provided. We find that a large asymmetry cannot be accommodated by heavy new
physics that does not interfere with the standard model. We show that a smoking
gun test for the heavy new physics hypothesis is a significant deviation from
the standard model prediction for the t \bar t differential cross section at
large invariant mass. At M_{t\bar t}>1 TeV the cross section is predicted to be
at least twice that of the SM at the Tevatron, and for M_{t\bar t}>1.5 TeV at
least three times larger than the SM at the LHC.
