Measurement of charm and beauty production at central rapidity versus charged-particle multiplicity in proton-proton collisions at \(\sqrt{s}\) = 7 TeV

Abstract

Prompt D meson and non-prompt J/\(\psi\) yields are studied as a function of the multiplicity of charged particles produced in inelastic proton-proton collisions at a centre-of-mass energy of \(\sqrt{s}=7\) TeV. The results are reported as a ratio between yields in a given multiplicity interval normalised to the multiplicity-integrated ones (relative yields). They are shown as a function of the multiplicity of charged particles normalised to the average value for inelastic collisions (relative charged-particle multiplicity). D\)^0\), D\)^+\) and D\)^{*+}\) mesons are measured in five \(p_{\rm T}\) intervals from 1 to 20 GeV/\(c\) and for \(|y|<0.5\) via their hadronic decays. The D-meson relative yield is found to increase with increasing charged-particle multiplicity. For events with multiplicity six times higher than the average multiplicity of inelastic collisions, a yield enhancement of a factor about 15 relative to the multiplicity-integrated yield in inelastic collisions is observed. The yield enhancement is independent of transverse momentum within the uncertainties of the measurement. The D\)^0\)-meson relative yield is also measured as a function of the relative multiplicity at forward pseudorapidity. The non-prompt J/\(\psi\), i.e. the B hadron, contribution to the inclusive J/\(\psi\) production is measured in the di-electron decay channel at central rapidity. It is evaluated for \(p_{\rm T}>1.3\) GeV/\(c\) and \(|y|<0.9\), and extrapolated to \(p_{\rm T}>0\), The fraction of non-prompt J/\(\psi\) in the inclusive J/\(\psi\) yields shows no dependence on the charged-particle multiplicity at central rapidity. Charm and beauty hadron relative yields exhibit a similar increase with increasing charged-particle multiplicity. The measurements are compared to PYTHIA 8, EPOS 3 and percolation calculations.