Abstract
We discuss production of charmed mesons in proton-proton collisions at the LHC. The cross section for inclusive production of cc pairs is calculated in the frame-work of the k ⊥ -factorization approach which effectively includes next-to-leading order corrections. Theoretical uncertainties of the model related to the choice of renormalization and factorization scales as well as due to the quark mass are discussed. Results of the k ⊥ -factorization approach are compared to NLO parton model predictions. The hadronization of charm quarks is included with the help of the Peterson fragmentation functions. Inclusive differential distributions in transverse momentum for several charmed mesons ( D 0 , D ± , D s ± ) are calculated and compared to recent results of the ALICE, ATLAS and LHCb collaborations. Furthermore, we also discuss production of two pairs cc of within a simple formalism of double-parton scattering (DPS). Surprisingly large cross sections, comparable to single-parton scattering (SPS) contribution, are predicted for LHC energies. We compare our predictions for double charm production ( DD meson-meson pairs) with recent results of the LHCb collaboration for azimuthal angle ϕ DD and rapidity distance between mesons Y DD . Meson-meson kinematical correlations are also confronted with those related to the standard meson-antimeson measurements. Our calculations clearly confirm the dominance of DPS in the production of events with double charm, however some strength seems to be still lacking. Possible missing contribution within the framework of single-ladder-splitting DPS mechanism is also discussed.
Highlights
ATLAS [1], ALICE [2, 3] and LHCb [4] collaborations have measured inclusive distributions for different charmed mesons
The LHCb collaboration has measured in addition a few correlation observables for charmed meson-antimeson pairs in the forward region 2 < y < 4 [5]
In the exploration of heavy quark production the main efforts concentrate on inclusive distributions
Summary
ATLAS [1], ALICE [2, 3] and LHCb [4] collaborations have measured inclusive distributions for different charmed mesons. In this approach the transverse momenta of incident partons are explicitly taken into account and their emission is encoded in the unintegrated gluon distributions (UGDFs) This allows to construct different correlation distributions which are strictly related to the transverse momenta of initial particles. In the th√e of DD meson-meson pairs at LHCb collaboration s = 7 TeV which is surprisingly large, including interesting correlation distributions [5] Those data sets for double open charm production have been studied differentially only within the k⊥-factorization approach using unintegrated gluon distributions [8], where several observables useful to identify the DPS effects in the case of double open charm production have been carefully discussed. In order to draw definite conclusions about the DPS effects in double charm production it is necessary to estimate contribution to ccccfinal state from the standard mechanism of single-parton scattering [9]
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