Azimuthal decorrelations and multiple parton interactions in photon+2 jet and photon+3 jet events in ppbar collisions at sqrt{s}=1.96 TeV

TL;DR

This paper measures azimuthal decorrelations in photon+jets events in proton-antiproton collisions at 1.96 TeV, comparing results to MPI models in PYTHIA and SHERPA, and identifying contributions from double parton interactions.

Contribution

It provides the first detailed measurement of azimuthal decorrelations in photon+2 and photon+3 jet events at Tevatron energies, testing MPI models against experimental data.

Findings

Data show significant contribution from double parton interactions.

PYTHIA and SHERPA MPI models accurately describe the observed decorrelations.

Fraction of double parton events varies with azimuthal angle and jet pT.

Abstract

Samples of inclusive photon+2 jet and photon+3 jet events collected by the D0 experiment with an integrated luminosity of about 1fb^-1 in ppbar collisions at sqrt{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 (pT) of the photon+leading jet system (jets are ordered in pT) and pT of the other jet for photon+2 jet, or pT sum of the two other jets for photon+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 pT-ordered showers and by SHERPA with the default MPI model. The photon+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 pT.