Measurement of the D+ -meson production cross section at low transverse momentum in pp¯ collisions at s=1.96 TeV

We report on a measurement of the D+-meson production cross section as a function of transverse momentum (pT) in proton-antiproton (pp) collisions at 1.96 TeV center-of-mass energy, using the full data set collected by the Collider Detector at Fermilab in Tevatron Run II and corresponding to 10 fb-1 of integrated luminosity. We use D+→K-π+π+ decays fully reconstructed in the central rapidity region |y|<1 with transverse momentum down to 1.5 GeV/c, a range previously unexplored in pp collisions. Inelastic pp-scattering events are selected online using minimally biasing requirements followed by an optimized offline selection. The K-π+π+ mass distribution is used to identify the D+ signal, and the D+ transverse impact-parameter distribution is used to separate prompt production, occurring directly in the hard-scattering process, from secondary production from b-hadron decays. We obtain a prompt D+ signal of 2950 candidates corresponding to a total cross section σ(D+,1.5<pT<14.5 GeV/c,|y|<1)=71.9±6.8(stat)±9.3(syst) μb. While the measured cross sections are consistent with theoretical estimates in each pT bin, the shape of the observed pT spectrum is softer than the expectation from quantum chromodynamics. The results are unique in pp collisions and can improve the shape and uncertainties of future predictions.