Heavy-quark azimuthal momentum correlations as a sensitive probe of thermalization

In high-energy nuclear collisions the degree of thermalization at the partonic level is a key issue. Due to their large mass, heavy quarks and their possible participation in the collective flow of the QCD-medium constitute a powerful probe for thermalization. We present studies with PYTHIA for pp collisions at the top LHC energy of applying the two-particle transverse momentum correlator 〈Δpt,1,Δpt,2〉 to pairs of heavy-quark hadrons and their semi-leptonic decay products as a function of their relative azimuth. Modifications or even the complete absence of initially existing correlations in Pb+Pb collisions might indicate thermalization at the partonic level.