  Multiple Parton Interactions are the tool to obtain information on the
correlations between partons in the hadron structure. Partons may be correlated
in all degrees of freedom and all different correlation terms contribute to the
cross section. The contributions due to the different parton flavors can be
isolated, at least to some extent, by selecting properly the final state. In
the case of high energy proton-proton collisions, the effects of correlations
in the transverse coordinates and in fractional momenta are, on the contrary,
unavoidably mixed in the final observables. The standard way to quantify the
strength of double parton interactions is by the value of the effective cross
section and a small value of the effective cross section may be originated both
by the relatively short transverse distance between the pairs of partons
undergoing the double interaction and by a large dispersion of the distribution
in multiplicity of the multi-parton distributions. The aim of the present paper
is to show how the effects of longitudinal and transverse correlations may be
disentangled by taking into account the additional information provided by
double parton interactions in high energy proton-deuteron collisions.
