Azimuthal decorrelations and multiple parton interactions in γ+2 jet and γ+3 jet events in pp̅ collisions at √s=1.96 TeV

Abstract

Samples of inclusive γ+2 jet and γ+3 jet events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 in pp̅ collisions at √s=1.96 TeV are used to measure cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p_T) of the γ+leading jet system (jets are ordered in p_T) and p_T of the other jet for γ+2 jet, or p_T sum of the two other jets for γ +3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the pythia and sherpa Monte Carlo (MC) generators. The data indicate a contribution from events with double parton (DP) interactions and are well-described by predictions provided by the pythia MPI models with p_T-ordered showers and by sherpa with the default MPI model. The γ+2 jet data are also used to determine the fraction of events with DP interactions as a function of the azimuthal angle and as a function of the second jet p_T.