Constituent quarks, diquarks and the N − Δ mass splitting

We analyze hadron as well as quark and diquark correlation functions in Landau gauge in order to extract information on the spin dependence of the quark-quark interaction. We find evidence that the N − Δ mass splitting can be attributed to the spin dependence of the interaction between quarks in a colour anti-triplet state with spin 0 and 1, respectively. The lightest excitations are observed in the S = 0 channel. However, no evidence for a deeply bound diquark state is found.