Special features of heavy quark-antiquark pair production ratios at LHC
  We consider the ratio of the cross section of production of heavy bottom-antibottom pairs ($\sigma_{b\bar b}$) to the cross section of production of top-antitop pairs ($\sigma_{t\bar t}$) at LHC. We show that in this ratio a major fraction of virtual contributions (including QCD components) disappears, leaving a residual dominant electroweak Yukawa effect that might be strongly enhanced in the presence of supersymmetry. A quantitative numerical analysis of the size of the effect is also performed under the assumption of a relatively light supersymmetric scenario. 
M. Beccaria, F.M. Renard, C. Verzegnassi