We perform a model independent analysis on $q \bar{ q} \rightarrow t \bar{ t}$ using an effective lagrangian with dim-6 four-quark operators, and derive necessary conditions on new physics that are consistent with the $t\bar{ t}$ production cross section %($\sigma_{ t\bar{ t}}$) and and the forward-backward (FB) asymmetry ($A_{ \rm FB}$) measured at the Tevatron. We also propose a new FB spin-spin correlation that is strongly correlated with the $A_{ \rm FB}$, and discuss possible new physics scenarios that could generate such dim-6 operators.
Categories: hep-ph hep-ex