Longitudinal top polarization as a probe of a possible origin of forward-backward asymmetry of the top quark at the Tevatron

If the forward-backward (FB) asymmetry of top quark (AFB) observed at the Tevatron deviates from the SM prediction, there must be P-violating interactions in qq¯→tt¯. This new interaction will necessarily affect the top spin polarization. In this Letter, we perform a model independent analysis on the longitudinal (anti)top polarization (PL and P¯L) using an effective lagrangian with dim-6 four-quark operators relevant for qq¯→tt¯, and show that the P-odd observable corresponding to the polarization difference (PL−P¯L) gives important informations on the chiral structures of new physics that might be relevant to the AFB.