CMS-PAS-HIN-16-001

CMS-PAS-HIN-16-001
$\mathrm{D}^0$ meson nuclear modification factor in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV
CMS Collaboration
June 2016

Abstract: $\mathrm{D}^{0}$ meson production has been measured in pp and PbPb collisions at $\sqrt{s_{_{\text{NN}}}}=$ 5.02 TeV in the central rapidity, $ \|y\|< $ 1 , and in the transverse momentum range between 2 and 100 GeV$/c$ with the CMS detector at the LHC. The proton-proton dataset used for this analysis corresponds to an integrated luminosity of 25.8 pb$^{-1}$, while the PbPb dataset corresponds to 404 $\mu$b$^{-1}$. The measured D$^0$ spectrum in pp collisions is well described by perturbative QCD calculations. The nuclear modification factor $\mathrm{R}_{\rm AA}$, defined as the ratio between the corrected PbPb yield and the proton-proton cross-section scaled by the number of incoherent nucleon-nucleon collisions, was also measured. In the transverse momentum range $p_{\rm T} =$ 6-10 GeV$/c$, the $\mathrm{D}^{0}$ yield in the PbPb collisions is suppressed by a factor of 4-5 compared to the scaled proton-proton reference. At high $p_{\rm T}$, the suppression is significantly reduced, approaching roughly a factor of 1.5 for particles with $p_{\rm T}$ in the range 60-100 GeV$/c$. The measured $\mathrm{D}^{0}$ nuclear modification factor is compatible with the charged particle $\mathrm{R}_{\rm AA}$, within the experimental uncertainties.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 782 (2018) 474. The superseded preliminary plots can be found here.

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1-a: Examples of ${\mathrm {D}^{0}}$ candidate invariant mass distribution in pp (a) and PbPb collisions (b) at 5.02 TeV.
png pdf	Figure 1-b: Examples of ${\mathrm {D}^{0}}$ candidate invariant mass distribution in pp (a) and PbPb collisions (b) at 5.02 TeV.
png pdf	Figure 2: ${p_{\mathrm {T}}} $-differential cross section of prompt ${\mathrm {D}^{0}}$ mesons in pp collisions at ${\sqrt {s}} =$ 5.02 TeV compared to the FONLL predictions [5].
png pdf	Figure 3-a: Nuclear modification factor $\rm {\rm R_{AA}} $ as a function of ${p_{\mathrm {T}}}$ in the centrality range 0-100% (a) and 0-10% (b). The inclusive charged particle $\rm R_{AA}$ results are superimposed for equivalent event selections [21]. The ${\mathrm {D}^{0}}$ ${\rm R_{AA}}$ are also compared to the predictions from various theoretical calculations [22,23,24,25,26,27,28,29,30].
png pdf	Figure 3-b: Nuclear modification factor $\rm {\rm R_{AA}} $ as a function of ${p_{\mathrm {T}}}$ in the centrality range 0-100% (a) and 0-10% (b). The inclusive charged particle $\rm R_{AA}$ results are superimposed for equivalent event selections [21]. The ${\mathrm {D}^{0}}$ ${\rm R_{AA}}$ are also compared to the predictions from various theoretical calculations [22,23,24,25,26,27,28,29,30].

Summary

In this note, measurements of the prompt $\mathrm{D}^{0}$ production cross section and nuclear modification factor $\mathrm{R}_{\rm AA}$ in pp and PbPb collisions in the central rapidity region ($ |y|< $ 1) at $\sqrt{s_{_{\text{NN}}}}=$ 5.02 TeV from CMS are presented. The $\mathrm{R}_{\rm AA}$ of prompt $\mathrm{D}^{0}$ mesons is measured as a function of the $\mathrm{D}^{0}$ transverse momentum from 2 to 100 GeV/$c$ in two centrality ranges. The $\mathrm{D}^{0}$ $\mathrm{R}_{\rm AA}$ is found to be strongly suppressed in PbPb collisions when compared to the measured pp reference scaled by the number of binary nucleon-nucleon collisions. These measurements are consistent with the nuclear modification factors of charged hadrons in the corresponding centrality ranges.

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