Implications of the CDF $ t\bar{t} $ forward-backward asymmetry for hard top physics

Abstract

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 Λ, and perform a model-independent analysis up to $ \mathcal{O}\left( {{{1} \left/ {{{\Lambda^4}}} \right.}} \right) $ . 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\;{\text{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\;{\text{TeV}} $ at least three times larger than the SM at the LHC.