We compare results of exact calculations of single-parton scattering (SPS) and double-parton scattering (DPS) for production of $c\overline{c}c\overline{c}$ and for $D$ meson correlations. The SPS calculations are performed in collinear approximation with exact matrix element for $gg\to c\overline{c}c\overline{c}$ and $q\overline{q}\to c\overline{c}c\overline{c}$ subprocesses. It is shown that the contribution of gluon-gluon subprocess is about factor 50 larger than that for quark-antiquark annihilation. The new results are compared with results of previous calculation with the approximate matrix element for $gg\to c\overline{c}c\overline{c}$ in the high-energy approximation. The cross section for the present exact calculation is bigger only at small invariant masses and small rapidity difference between two $c$ quarks (or two $\overline{c}$ antiquarks). We compare correlations in rapidities of two $c$ (or two $\overline{c}$) for DPS and SPS contributions. Finally, we compare our predictions for $D$ mesons with recent results of the LHCb Collaboration for invariant mass, rapidity distance between mesons and dimeson invariant mass. The predicted shapes are similar to the measured ones, however, we still underpredict the experimental cross sections. Our new calculations clearly confirm the dominance of DPS in the production of events with double charm.

• Received 6 March 2014

DOI:https://doi.org/10.1103/PhysRevD.89.094019