Data driving the top quark forward--backward asymmetry with a lepton-based handle

We propose that, within the standard model, the correlation between the t (t) over bar forward-backward asymmetry A(t (t) over bar) and the corresponding lepton-based asymmetry A(t)-at the differential level-is strong and rather clean both theoretically and experimentally. Hence a combined measurement of the two distributions as a function of the lepton p(T), a direct and experimentally clean observable, would lead to a potentially unbiased and normalization-free test of the standard model prediction. To check the robustness of our proposal, we study how the correlation is affected by mismeasurement of the t (t) over bar system transverse momenta, acceptance cuts, and scale dependence and compare the results of MCFM, POWHEG (with and without PYTHIA showering), and SHERPA's CSSHOWER in first-emission mode. We find that the shape of the relative differential distribution A(t)(p(T)(l))[A(t (t) over bar)(p(T)(l))] is only moderately distorted, hence supporting the usefulness of our proposal. Beyond the first emission, we find that the correlation is not accurately captured by lowest-order treatment. We also briefly consider other differential variables such as the system transverse mass and the canonical t (t) over bar invariant mass. Finally, we study new physics scenarios where the correlation is significantly distorted and therefore can be more readily constrained or discovered using our method. DOI: 10.1103/PhysRevD.87.034039