Abstract
The transverse momentum (pT) spectrum of prompt D0 mesons and their antiparticles has been measured via the hadronic decay channels D0→K−π+ and D‾0→K+π− in pp and PbPb collisions at a centre-of-mass energy of 5.02 TeV per nucleon pair with the CMS detector at the LHC. The measurement is performed in the D0 meson pT range of 2–100GeV/c and in the rapidity range of |y|<1. The pp (PbPb) dataset used for this analysis corresponds to an integrated luminosity of 27.4 pb−1 (530 μb−1 ). The measured D0 meson pT spectrum in pp collisions is well described by perturbative QCD calculations. The nuclear modification factor, comparing D0 meson yields in PbPb and pp collisions, was extracted for both minimum-bias and the 10% most central PbPb interactions. For central events, the D0 meson yield in the PbPb collisions is suppressed by a factor of 5–6 compared to the pp reference in the pT range of 6–10GeV/c. For D0 mesons in the high-pT range of 60–100GeV/c, a significantly smaller suppression is observed. The results are also compared to theoretical calculations.
Highlights
Relativistic heavy ion collisions allow the study of quantum chromodynamics (QCD) at high energy density and temperature
The nuclear modification factor in pPb collisions (RpA) was found to be consistent within the 15–20% uncertainties with unity for pT from 2 to 24 GeV/c. This suggests that the suppression of D mesons observed in PbPb collisions cannot be explained in terms of initial-state effects but is mostly due to strong final-state effects induced by the quark-gluon plasma (QGP)
The result is compared to the prediction of fixed-order plus next-to-leading logarithmic (FONLL) and a general-mass variable flavour number scheme (GM-VFNS) [34,35,36] calculation
Summary
Relativistic heavy ion collisions allow the study of quantum chromodynamics (QCD) at high energy density and temperature. Heavy quarks are effective probes to study the properties of the deconfined medium created in heavy ion collisions These quarks are mostly produced in primary hard QCD scatterings with a production timescale that is shorter than the formation time of the QGP [4]. The nuclear modification factor in pPb collisions (RpA) was found to be consistent within the 15–20% uncertainties with unity for pT from 2 to 24 GeV/c This suggests that the suppression of D mesons observed in PbPb collisions cannot be explained in terms of initial-state effects but is mostly due to strong final-state effects induced by the QGP. In this Letter, the production of prompt D0 mesons in PbPb collisions at 5.02 TeV is measured for the first time up to a pT of 100 GeV/c, allowing one to study the properties of the in-medium energy loss in a new kinematic regime. The RAA is reported for two centrality intervals: in the inclusive sample (0–100%), and in one corresponding to the most overlapping 10% of the collisions
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