Measurement of prompt D0, D+, D*+, and $$ {\mathrm{D}}_{\mathrm{S}}^{+} $$ production in p–Pb collisions at $$ \sqrt{{\mathrm{s}}_{\mathrm{NN}}} $$ = 5.02 TeV

Abstract

The measurement of the production of prompt D 0 , D + , D * + , and D + s mesons in proton-lead (p-Pb) collisions at the centre-of-mass energy per nucleon pair of √ s 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 < y cms < 0.04) as a function of transverse momentum (p T) in the intervals 0 < p T < 36 GeV/c for D 0 , 1 < p T < 36 GeV/c for D + and D * + , and 2 < p T < 24 GeV/c for D + s mesons. For each species, the nuclear modification factor R pPb is calculated as a function of p T using a proton-proton (pp) reference measured at the same collision energy. The results are compatible with unity in the whole p T range. The average of the non-strange D mesons R pPb is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The p T dependence of the D 0 , D + , and D * + nuclear modification factors is also reported in the interval 1 < p T < 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 p T-differential cross sections of D 0 , D + , D * + , and D + s mesons are also reported. The D + s and D + yields are compared as a function of the charged-particle multiplicity for several p T intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties.

Measurement of electrons from heavy-flavour hadron decays as a function of multiplicity in p-Pb collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

“…Initially, it was assumed that a QGP is not formed in proton-nucleus (p-A) collisions, so these collisions were used as a baseline for measurements in A-A collisions to test for possible CNM effects. The ALICE Collaboration reported the p T -differential nuclear modification factor R pPb of D mesons [31,32] and electrons from heavy-flavour hadron decay [33] measured at midrapidity in p-Pb collisions at √ s NN = 5.02 TeV. The R pPb at midrapidity are consistent with unity and with theoretical calculations including CNM effects, indicating that CNM effects are small in this kinematic region.…”

“…Thus, if final-state effects are also present in p-Pb collisions, modification of the momentum distribution of heavy-flavour production could be expected in high-multiplicity p-Pb collisions. Recently, ALICE measured the p T -differential nuclear modification factor of D mesons for different multiplicity classes at midrapidity in p-Pb collisions at √ s NN = 5.02 TeV [32,45]. These works have shown that the D-meson results are consistent with binary collision scaling of the yield in pp collisions, within the statistical and systematic uncertainties.…”

Azimuthal correlations of prompt D mesons with charged particles in pp and p–Pb collisions at $$\varvec{\sqrt{s_\mathrm{NN}}} = 5.02\ \hbox {TeV}$$

“…A dedicated optimisation on the selection variables was done, where the selections were tightened to increase the signalto-background ratio of the D-meson invariant mass peaks. A gain up to a factor 5 at low p D T was obtained with respect to the selection defined in [25,62], at the expenses of a reduction of the raw yield. This allowed reducing the impact of the D-meson combinatorial background, whose subtraction induces the largest source of statistical uncertainty on the Associated particles are defined as charged primary particles with p assoc T > 0.3 GeV/c and with pseudorapidity |η| < 0.8.…”

“…The D mesons are reconstructed from the following hadronic decay channels: [61] in the transverse-momentum interval 3 < p T < 24 GeV/c. The D-meson selection strategy, described in detail in [25,62], exploits the displaced topology of the decay and utilises the particle identification capabilities of the TPC and TOF to select on the D-meson decay particles. A dedicated optimisation on the selection variables was done, where the selections were tightened to increase the signalto-background ratio of the D-meson invariant mass peaks.…”

“…The most relevant effect is a modification of the parton distribution functions due to nuclear shadowing [24], which can consequently affect the heavy-flavour production cross section. Measurements of the nuclear modification factor of D mesons and of electrons from heavy-flavour hadron decays in p-Pb collisions at √ s NN = 5.02 TeV [25,26] point towards a small influence of cold-nuclear-matter effects on the heavy-flavour quark production at midrapidity. Nevertheless, nuclear effects could still affect the fragmentation and hadronisation of heavy quarks.…”