Bound-state effects on top quark production at hadron colliders

We study bound-state effects on the tt-bar production cross section in the threshold region at hadron colliders. The bound-state effects are important particularly at the LHC where the gluon fusion is the dominant subprocess. Due to the formation of tt-bar resonances in the J=0 color-singlet channel of gg→tt-bar and the large width of the top quark, the tt-bar invariant-mass distribution peaks at a few GeV below the tt-bar threshold, and it is significantly enhanced over the naive NLO prediction until several GeV above the threshold. We present predictions of the tt-bar invariant-mass distribution which incorporate both the bound-state effects and initial-state radiations up to NLO. The bound-state effects would lead to a substantial deformation of top-quark kinematical distributions in the threshold region