Measurement of charm and beauty production at central rapidity versus charged-particle multiplicity in proton-proton collisions at $\mathbf{\sqrt{{\textit s}}}=7$ 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.
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Journal of High Energy Physics, Springer, 2015, 09, pp.148. 〈10.1007/JHEP09(2015)148〉
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Soumis le : mardi 5 mai 2015 - 08:24:13
Dernière modification le : mardi 19 juin 2018 - 01:19:47

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J. Adam, G. Conesa Balbastre, J. Faivre, C. Furget, R. Guernane, et al.. Measurement of charm and beauty production at central rapidity versus charged-particle multiplicity in proton-proton collisions at $\mathbf{\sqrt{{\textit s}}}=7$ TeV. Journal of High Energy Physics, Springer, 2015, 09, pp.148. 〈10.1007/JHEP09(2015)148〉. 〈in2p3-01148625〉

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