CMS-HIN-21-003

CMS-HIN-21-003 ; CERN-EP-2022-219
Measurements of azimuthal anisotropy of nonprompt D $^{0}$ mesons in PbPb collisions at $\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}=$ 5.02 TeV
CMS Collaboration
3 December 2022
Phys. Lett. B 850 (2024) 138389
Abstract: Measurements of the elliptic ( $v_{2}$ ) and triangular ( $v_{3}$ ) azimuthal anisotropy coefficients are presented for D $^{0}$ mesons produced in b hadron decays (nonprompt D $^{0}$ mesons) in lead-lead collisions at $\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}=$ 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt D $^{0}$ mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb $^{-1}$ . Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt D $^{0}$ mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of $v_{2}$ and $v_{3}$ and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt D $^{0}$ mesons. By comparing to theoretical predictions, the results imply that there is a mass hierarchy of quark interactions with the medium.
Links: e-print arXiv:2212.01636 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: An example of the fit to the invariant mass spectrum (left panel) and an example of the template fit of the inclusive D $^{0}$ meson yields, extracted as a function of DCA (right panel). The former fit is used for determining the total D $^{0}$ yields and the latter for determining the fraction of nonprompt D $^{0}$ mesons.
png pdf	Figure 1-a: An example of the fit to the invariant mass spectrum (left panel) and an example of the template fit of the inclusive D $^{0}$ meson yields, extracted as a function of DCA (right panel). The former fit is used for determining the total D $^{0}$ yields and the latter for determining the fraction of nonprompt D $^{0}$ mesons.
png pdf	Figure 1-b: An example of the fit to the invariant mass spectrum (left panel) and an example of the template fit of the inclusive D $^{0}$ meson yields, extracted as a function of DCA (right panel). The former fit is used for determining the total D $^{0}$ yields and the latter for determining the fraction of nonprompt D $^{0}$ mesons.
png pdf	Figure 2: The elliptic, $v_{2}$ (upper panels), and the triangular, $v_{3}$ (lower panels), flow coefficients of nonprompt and prompt (from Ref. [18]) D $^{0}$ mesons as functions of their $p_{\mathrm{T}}$ and in three bins of centrality. The bars and the boxes represent statistical and systematic uncertainties, respectively.
png pdf	Figure 3: The elliptic, $v_{2}$ (upper panel), and the triangular, $v_{3}$ (lower panel), flow coefficients of nonprompt D $^{0}$ mesons as functions of their $p_{\mathrm{T}}$ and in three bins of centrality. The bars and the boxes represent statistical and systematic uncertainties, respectively. The colored bands show theoretical predictions [49-56].

Summary

In summary, the elliptic (

$v_{2}$ ) and triangular (

$v_{3}$ ) flow harmonics of D

$^{0}$ mesons that originate in b hadron decays (nonprompt D

$^{0}$ mesons) are measured in lead-lead collisions at

$\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}}=$ 5.02 TeV. The

$v_{2}$ results show a weak transverse momentum (

$p_{\mathrm{T}}$ ) dependence and suggest a slight increase for more peripheral collisions. An indication of a nonzero

$v_{3}$ coefficient is found for nonprompt D

$^{0}$ mesons with 4

$< p_{\mathrm{T}} <$ 6 GeV/

$c$ . The magnitudes of the flow coefficients are lower for nonprompt D

$^{0}$ than for prompt D

$^{0}$ mesons. This magnitude difference is more pronounced in the case of

$v_{2}$ . Comparisons of the results to theoretical models suggest a mass hierarchy in quark interactions with the quark-gluon plasma, thereby extending our understanding of heavy quark interactions with the medium.

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