This book mainly focuses on the study of photon + 3 jets final state in Proton-Proton Collisions at √s = 7TeV,  searching for patterns of two (or more) distinct hard scatterings in the same collision, i.e the so-called Double Parton Scattering (DPS). A new method by using Monte Carlo generators was performed and provides higher order corrections to the description of the Single Parton Scattering (SPS) background. Further it is investigated whether additional contributions from DPS can improve the agreement between the measured data and the Monte Carlo predictions. The current theoretical uncertainties related to the SPS background are found ... Read moreto be larger than expectation. At the same time a rich set of DPS-sensitive measurements is reported for possible further interpretation.