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We discuss production of $D^0 D^0$ (and ${\bar D}^0 {\bar D}^0$) pairsrelated to the LHCb Collaboration results for $\sqrt{s}$ = 7 TeV inproton-proton scattering. We consider double-parton scattering (DPS) mechanismsof double $c \bar c$ production and subsequent $cc \to D^{0}D^{0}$hadronization as well as double $g$ and mixed $g c\bar c $ production with $gg\to D^{0}D^{0}$ and $gc \to D^{0}D^{0}$ hadronization calculated with the helpof the scale-dependent hadronization functions of Kniehl et al. Single-partonscattering (SPS) mechanism of digluon production is also taken into account. Wecompare our results with several correlation observables in azimuthal angle$\varphi_{D^{0}D^{0}}$ between $D^{0}$ mesons or in dimeson invariant mass$M_{D^{0}D^{0}}$. The inclusion of new mechanisms with $g \to D^{0}$fragmentation leads to larger cross sections, than when including only DPSmechanism with standard scale-independent $cc \to D^{0}D^{0}$ fragmentationfunctions. Some consequences of the presence of the new mechanisms arediscussed. In particular a larger $\sigma_{eff}$ is needed to describe the LHCbdata. There is a signature that $\sigma_{eff}$ may depend on transversemomentum of $c$ quarks and/or $\bar c$ antiquarks.

New mechanisms for double charmed meson production at the LHCb