Abstract
Recently the CDF and the D0 Collaborations presented the data on the top forward–backward (FB) asymmetry AFB as functions of Mtt¯ and Δy≡yt−yt¯. We study these observables in the effective Lagrangian approach with dimension-6 qq¯tt¯ contact interactions, and compare with the CDF and D0 data. When we stay within the validity region of the effective Lagrangian approach, the mass dependent top FB asymmetry turns out to be smaller than the CDF data, more than 2-σ away. If this discrepancy remains in the future data with better statistics, it would imply that the effective Lagrangian approach is not adequate for the top FB asymmetry, and a new physics scale around a few hundred GeV in the t- or u-channel may be responsible for the observed top FB asymmetry.
Highlights
The top forward-backward (FB) asymmetry (AFB) measured at the Tevatron has been an interesting subject, since it may indicate a new physics around the corner
In our previous papers [4, 5], we used the integrated FB asymmetry in order to extract information on the possible new physics scenarios and could discriminate a class of models from another, in the limit where new physics scale is beyond the reach of the Tevatron
The reconstructed values of AFB with two-bin analysis in Mttshow the flatter and smaller asymmetry than the CDF data, see Table II. They are at the reconstructed level and cannot be compared directly to the theoretical predictions. In this Addendum to Ref. [4], we present the predictions for the AFB as functions of Mttand ∆y ≡ yt − ytwithin the effective Lagrangian approach with dim-6 contact interactions for qq → tt [4, 5]: L6
Summary
The top forward-backward (FB) asymmetry (AFB) measured at the Tevatron has been an interesting subject, since it may indicate a new physics around the corner. If the measured AFB(Mtt) changes its shape and decreases at some scale after unfolding, it would indicate that our approach based on the dim-6 effective Lagrangian is not a good one. If this discrepancy in the mass dependent FB asymmetry remains even if more data is accumulated and analyzed and the central value of the integrated top FB asymmetry is more or less the same as the current value Eq (1), it would indicate that the effective Lagrangian approach may not give a proper description for the top FB asymmetry at the Tevatron [25] In such a case, it is very likely that the mass dependent (or ∆y dependent) FB asymmetry shows nonlinear behavior, changing the shape
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