QCD predictions for open charm meson production at the LHCb in a fixed-target experiment

We investigate open charm meson production in fixed-target LHCb experiment at s=86.6 GeV in p+He4 collisions. Theoretical calculations of charm cross section are done in the framework of the kT-factorization approach. Its application in the kinematical range never examined before is carefully discussed. We consider different schemes for the calculations relevant for different unintegrated (transverse momentum dependent) parton densities in a proton. We include in the analysis both Catani-Ciafaloni-Fiorani-Marchesini (CCFM)—and Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP)-based models of unintegrated parton distributions appropriate for the considered kinematics. Integrated as well as differential cross sections as a function of D0 meson rapidity and transverse momentum are shown and compared with the experimental data. As a reference point, predictions of next-to-leading order collinear approach are also presented and discussed. A very good agreement between the experimental data and the kT-factorization predictions was obtained. Both the CCFM and the DGLAP-based frameworks for parton distributions in a proton are successfully used to explain the LHCb fixed-target open charm cross section.