Four-jet production in the $k_t$-factorisation
  We discuss the single-parton and double-parton scattering (SPS or DPS) effects in four-jet production at the LHC. The calculations of both single-parton and double-parton scattering components are done in the high-energy (or $k_{T}$)-factorization approach. Here we follow our recent developments of relevant methods and tools. The calculations are performed for kinematical situations relevant for two experimental measurements (ATLAS and CMS) at the LHC. We compare our results to those reported by the ATLAS and CMS collaborations for different sets of kinematical cuts. A special attention is given to the optimization of kinematical conditions in order to enhance the relative contribution of DPS in four-jet sample. Several differential distributions are calculated and carefully discussed in the context of recent and future searches for DPS effects at the LHC. The dependences of the relative DPS amount is studied as a function of rapidity of jets, rapidity distance, and various azimuthal correlations between jets. The regions with an enhanced DPS contribution are identified. 
Antoni Szczurek and Rafal Maciula
hep-ph