Correlations in Multi-Parton Interactions
  In double parton interactions, the two hard proceses are correlated via double parton densities. We examine the double Drell-Yan process and the impact of such correlations on the differential cross section. In particular correlations between the spins of the interacting quarks can induce correlations between the decay planes of the vector bosons. We investigate upper limits on spin correlations following from positivity of the double parton densities. 
Tomas Kasemets
hep-ph nucl-th