On the ratio of ttbb and ttjj cross sections at the CERN Large Hadron   Collider
  Triggered by ongoing experimental analyses, we report on a study of the cross section ratio sigma(pp -> ttbb)/sigma(pp -> ttjj) at the next-to-leading order in QCD, focusing on both present and future collider energies: sqrt{s}= 7, 8, 13 TeV. In particular, we provide a comparison between our predictions and the currently available CMS data for the 8 TeV run. We further analyse the kinematics and scale uncertainties of the two processes for a single set of parton distribution functions, with the goal of assessing possible correlations that might help to reduce the theoretical error of the ratio and thus enhance the predictive power of this observable. We argue that the different jet kinematics makes the ttbb and ttjj processes uncorrelated in several observables, and show that the scale uncertainty is not significantly reduced when taking the ratio of the cross sections. 
G. Bevilacqua and M. Worek
hep-ph hep-ex