Evidence in favor of single parton scattering mechanism in γ and D associated production at the LHC

Associated production of prompt gamma(1S) and D-+,D-0 mesons has been proposed as a golden channel for the search of double parton scattering, because single parton scattering contribution to the cross section is believed to be negligible on the basis of leading-order calculations in the collinear parton model. We study this process in the leading-order approximation of the parton Reggeization approach. Hadronization of a b (b) over bar pair into bottomonium states is described within the framework of the nonrelativistic QCD-factorization approach, while production of D mesons is described in the fragmentation model with scale-dependent fragmentation functions. We have found good agreement with LHCb data for various normalized differential distributions, except for the case of spectra on azimuthal angle differences at the small Delta phi values. Crucially, the total cross section in our single parton scattering model accounts for more than one-half of observed cross sections, thus dramatically shrinking the room for the double parton scattering mechanism.