Mass dependent top forward backward asymmetry in the effective Lagrangian approach: Addendum to 'Model independent analysis of the forward-backward asymmetry of top quark production at the Tevatron'

摘要

Recently the CDF and the D0 Collaborations presented the data on the topforward-backward (FB) asymmetry A_FB as functions of M_(t t^bar) and \Delta y =y_t - y_t^bar. We study these observables in the effective Lagrangian approachwith dimension-6 q q^bar t t^bar contact interactions, and compare with the CDFand D0 data. When we stay within the validity region of the effectiveLagrangian approach, the mass dependent top FB asymmetry turns out to besmaller than the CDF data, more than 2-sigma away. If this discrepancy remainsin the future data with better statistics, it would imply that the effectiveLagrangian approach is not adequate for the top FB asymmetry, and a new physicsscale around a few hundred GeV in the t- or u-channel may be responsible forthe observed top FB asymmetry.