New mechanisms for double charmed meson production at the LHCb

We discuss production of D0D0D0D0 (and D¯0D¯0) pairs related to the LHCb Collaboration results for s=7 TeV in proton–proton scattering. We consider double-parton scattering (DPS) mechanisms of double cc¯ production and subsequent cc→D0D0cc→D0D0 hadronization as well as double g   and mixed gcc¯ production with gg→D0D0gg→D0D0 and gc→D0D0gc→D0D0 hadronization calculated with the help of the scale-dependent hadronization functions of Kniehl et al. Single-parton scattering (SPS) mechanism of digluon production is also taken into account. We compare our results with several correlation observables in azimuthal angle φD0D0φD0D0 between D0D0 mesons or in dimeson invariant mass MD0D0MD0D0. The inclusion of new mechanisms with g→D0g→D0 fragmentation leads to larger cross sections, than when including only DPS mechanism cc→D0D0cc→D0D0 with standard scale-independent fragmentation functions. Some consequences of the presence of the new mechanisms are discussed. In particular a larger σeffσeff is needed to describe the LHCb data. There is a signature that σeffσeff may depend on transverse momentum of c   quarks and/or c¯ antiquarks.