Abstract
The measurement of the production of prompt D0, D+, D*+, and {mathrm{D}}_{mathrm{S}}^{+} mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of sqrt{s_{mathrm{NN}}} = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb−1, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 < ycms< 0.04) as a function of transverse momentum (pT) in the intervals 0 < pT< 36 GeV/c for D0, 1 < pT< 36 GeV/c for D+ and D*+, and 2 < pT< 24 GeV/c for D+ mesons. For each species, the nuclear modification factor RpPb is calculated as a function of pT using a proton-proton (pp) ref- erence measured at the same collision energy. The results are compatible with unity in the whole pT range. The average of the non-strange D mesons RpPb is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The pT dependence of the D0, D+, and D*+ nuclear modification factors is also reported in the interval 1 < pT< 36 GeV/c as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the pT-differential cross sections of D0, D+, D*+, and {mathrm{D}}_{mathrm{S}}^{+} mesons are also reported. The {mathrm{D}}_{mathrm{S}}^{+} and D+ yields are compared as a function of the charged-particle multiplicity for several pT intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties.
Highlights
Can describe within uncertainties the production cross sections of D and B mesons measured in pp and pp collisions in different kinematic regions at centre-of-mass energies from 0.2 to 13 TeV
The angular correlations in high-multiplicity p–Pb collisions were found to have similar properties as those observed in Pb–Pb collisions, where they are commonly interpreted as indications of a collective particle flow produced during the hydrodynamic evolution of the Quark-Gluon Plasma (QGP) [39,40,41,42]
Hydrodynamic calculations, that assume the formation of a medium with some degree of collectivity, can describe the angular correlations measured in p–Pb collisions, which suggests a common hydrodynamic origin of the experimental observations from small to large collision systems
Summary
The ALICE apparatus [66] is composed of a central barrel comprising various detectors for particle reconstruction and identification at mid-rapidity (|η| < 0.9), a forward muon spectrometer (−4 < η < −2.5), and a set of forward-backward detectors for triggering and event characterisation. During the p–Pb data-taking period, the beam energies were 4 TeV for protons and 1.58 TeV per nucleon for lead nuclei With this beam configuration, the nucleon–nucleon centre-of-mass system moves in rapidity by ∆ycms = 0.465 in the direction of the proton beam. The events were classified according to the energy deposited in the ZDC positioned in the Pb-going side by the neutrons produced in the interaction by nuclear de-excitation processes, or knocked out by wounded nucleons. The multiplicity of these neutrons is expected to grow monotonically with the number of nucleon–nucleon binary collisions, Ncoll.
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