Measurement of color flow in t-tbar events from p-pbar collisions at   sqrt(s)=1.96 TeV
  We present the first measurement of the color representation of the hadronically decaying W boson in t-tbar events, from 5.3 fb^-1 of integrated luminosity collected with the D0 experiment. A novel calorimeter-based vectorial variable, "jet pull," is used, sensitive to the color-flow structure of the final state. We find that the fraction of uncolored W bosons is 0.56 +- 0.42(stat+syst), in agreement with the standard model. 
D0 Collaboration, V. Abazov, et al
hep-ex