pQCD physics of multiparton interactions

We study production of two pairs of jets in hadron-hadron collisions in view of extracting contribution of double hard interactions of three and four partons (3→4, 4→4). Such interactions, in spite of being power suppressed at the level of the total cross section, become comparable with the standard hard collisions of two partons, 2→4, in the back-to-back kinematics when the transverse momentum imbalances of two pairing jets are relatively small. We express differential and total cross sections for two-dijet production in double parton collisions through the generalized two-parton distributions, ₂GPDs (Block et al., Phys. Rev. D 83, 071501, 2011), and treat them in the leading logarithmic approximation of pQCD that resums collinear logarithms in all orders. A special emphasis is given to 3→4 double hard interaction processes which, being of the same order in α_S as the 4→4 process, turn out to be geometrically enhanced compared to the latter and should contribute significantly to four-jet production. The framework developed here takes into systematic consideration perturbative Q² evolution of ₂GPDs. It can be used as a basis for future analysis of NLO corrections to multiparton interactions (MPI) at LHC and Tevatron colliders, in particular for improving evaluation of QCD backgrounds to new physics searches.