Open charm meson production at LHC
  We discuss charm production at the LHC. The production of single $c \bar c$ pairs is calculated in the $k_t$-factorization approach. We use Kimber-Martin-Ryskin unintegrated gluon distributions in the proton. The hadronization is included with the help of Peterson fragmentation functions. Transverse momentum and pseudorapidity distributions of charmed mesons are presented and compared to recent results of the ALICE, LHCb and ATLAS collaborations. Furthermore we discuss production of two pairs of $c \bar c$ within a simple formalism of double-parton scattering (DPS). Surprisingly large cross sections, comparable to single-parton scattering (SPS), are predicted for LHC energies. We discuss perspectives how to identify the double scattering contribution. We predict much larger cross section for large rapidity distance between charm quarks from different hard parton scatterings compared to single scattering. 
Rafal Maciula, Marta Luszczak, Antoni Szczurek
hep-ph hep-ex