Study of double parton interactions in photon + 3 jets events and photon + $b/c$ + 2 jets events at the Tevatron

We have used a sample of photon + 3 jets as well as photon + $b/c$ + 2 jet events collected by the D0 experiment with an integrated luminosity of 8.7 fb$^{-1}$ to determine the fraction of events with hard double parton (DP) scattering in a single proton-antiproton collision at $\sqrt{s}=1.96$ TeV. The DP fraction and effective cross section, a process-independent scale parameter related to the parton density inside the nucleon, are measured in the kinematic region $p_{\rm T}^{\gamma}>$26 GeV, $p_{\rm T}^{\rm jet1}>$15 GeV, and 15 $\leq p_{\rm T}^{\rm jet2,3}\leq$ 35 GeV.