Production of one and two ccˉc \bar c pairs at LHC

We report on charm production at LHC. The production of single $c \bar c$ pairs is calculated in the $k_t$-factorization approach with different unintegrated gluon distributions. Examples of transverse momentum distributions for charmed mesons are presented and compared to recent experimental results from LHC. Some missing strength is observed for most of UGDFs. Furthermore we discuss production of two $c \bar c$ pairs within double-parton scattering (DPS) and single-parton scattering (SPS) mechanisms. Surprisingly large cross sections, comparable to single $c \bar c$ pair production are predicted. We discuss first experimental results from LHCb collaboration on production of pairs of $D$ mesons of the same flavour.Comment: 5 pages, 4 figures, invited talk by A. Szczurek at the international workshop Diffraction2012, Puerto del Carmen, Lanzarote, Spain, September 10-15, 201

Can the triple-parton scattering be observed in open charm meson production at the LHC?

We investigate whether the triple-parton scattering effects can be observed in open charm production in proton-proton collisions at the LHC. We use so-called factorized Ansatz for calculations of hard multiple-parton interactions. The numerical results for each parton interaction are obtained within the $k_{T}$-factorization approach. Predictions for one, two and three $c\bar c$ pairs production are given for $\sqrt{s}= 7$ TeV and $\sqrt{s}= 13$ TeV. Quite large cross sections, of the order of milibarns, for the triple-parton scattering mechanism are obtained. We suggest a measurement of three $D^{0}$ mesons or three $\bar{D^{0}}$ antimesons by the LHCb collaboration. Confronting our results with recent LHCb experimental data for single and double $D^{0}$ (or $\bar{D^{0}}$) meson production we present our predictions for triple meson final state: $D^{0}D^{0}D^{0}$ or $\bar{D^{0}}\bar{D^{0}}\bar{D^{0}}$. We present cross sections for the LHCb fiducial volume as well as distributions for $D^{0}$ meson transverse momentum and three-$D^{0}$ meson invariant mass. The predicted visible cross sections, including the detector acceptance, hadronization effects and $c \to D^{0}$ branching fraction, is of the order of a few nanobarns. The counting rates including $D^{0} \to K^{-}\pi^{+}$ branching fractions are given for known or expected integrated luminosities.Comment: 12 pages, 4 figure