Top Antitop Mass difference

We update the previous D0 measurement of the mass difference between top and antitop quarks in lepton+jets final states produced in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV. The $t\bar{t}$ purity of the lepton+jets sample is enhanced by applying a neural-network-based $b$-tagging technique. Using the Matrix Element approach developed at D0, the combination of the e+jets and mu+jets channels in data corresponding to 3.6 fb$^{-1}$, is used to extract a $t\bar{t}$ mass difference.