  We briefly discuss the status of double parton scattering (DPS) on both
theoretical and experimental sides and summarize the state of the naive DPS
model, where the scatterers are taken completely independent. We then elaborate
on some of the effects which are neglected in such an approach, and often
ignored in phenomenological studies, with focus on polarization - which arises
from the correlation between the spin of two partons inside a proton.
Polarization is of particular interest, thanks to its direct and calculable
connections to the distribution of particles in the final state. Although the
physics described is different, there are strong similarities between
polarization in DPS and in single partons scattering with measured transverse
momentum, and several of the techniques and results from studies of transverse
momentum dependent parton distributions can be translated into the setting of
double parton scattering.
