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

J. Adam , G. Conesa Balbastre (1) , J. Faivre (1) , C. Furget (1) , R. Guernane (1) , S. Kox (1) , J.S. Real (1) , C. Silvestre , A. Vauthier (1) , R. Vernet (2) , I. Belikov (3) , B. Hippolyte (3) , C. Kuhn (3) , A. Maire (3) , L. Molnar (3) , C. Roy (3) , X. Sanchez Castro (3) , Laurent Aphecetche (4) , Guillaume Batigne (4) , B. Erazmus (4) , Magali Estienne (4) , Marie Germain (4) , J. Martin Blanco (4) , Gines Martinez Garcia (4) , L. Massacrier (4) , A. Morreale (4) , Philippe Pillot (4) , L. Ronflette (4) , Y. Schutz (4) , Alexandre Shabetai (4) , Diego Stocco (4) , M. Wang (4) , J. Zhu (4) , C. Cheshkov (5) , B. Cheynis (5) , L. Ducroux (5) , J.-Y. Grossiord (5) , B. Teyssier (5) , R. Tieulent (5) , A. Uras (5) , Z. Conesa Del Valle (6) , I. Das (6) , B. Espagnon (6) , C. Hadjidakis (6) , I. Lakomov (6) , C. Suire (6) , J. D. Tapia Takaki (6) , L. Valencia Palomo (6)

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 CC-IN2P3 - Centre de Calcul de l'IN2P3
3 IPHC - Institut Pluridisciplinaire Hubert Curien
4 SUBATECH - Laboratoire SUBATECH Nantes
5 IPNL - Institut de Physique Nucléaire de Lyon
6 IPNO - Institut de Physique Nucléaire d'Orsay

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.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des Hautes Energies - Expérience [hep-ex]

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, 2015, 09, pp.148. ⟨10.1007/JHEP09(2015)148⟩. ⟨in2p3-01148625⟩