CMS-PAS-HIN-21-003

CMS-PAS-HIN-21-003
Azimuthal anisotropy of nonprompt D$^{0}$ mesons in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 5.02 TeV
CMS Collaboration
April 2022

Abstract: The azimuthal anisotropy elliptic ($v_2$) and triangular ($v_3$) Fourier coefficients of D$^{0}$ mesons produced in B hadron decays are measured in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 5.02 TeV. Due to the larger bottom quark mass as compared to the charm quark mass, separate measurements of charm and bottom hadron azimuthal anisotropy can shed new light on understanding the mass dependence of the heavy quark and medium interaction. The results show lower magnitude of $v_2$ and $v_3$ and significantly weaker dependence on transverse momentum and centrality than those found for non-decay D$^{0}$ mesons. A non-zero $v_3$ coefficient of the D$^{0}$ mesons from B decay is observed. Obtained results are in qualitative agreement with theoretical predictions.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PLB. The superseded preliminary plots can be found here.

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) are shown.
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) are shown.
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) are shown.
png pdf	Figure 2: The elliptic, $v_2$, (top panel) and the triangular, $v_3$, (bottom panel) flow coefficient of nonprompt and prompt (from [14]) D$^{0}$ mesons as functions of $p_{\mathrm {T}}$ and in three bins of centrality. The bars and the boxes represent statistical and systematic uncertainties, respectively.
png pdf	Figure 3: The elliptic, $v_2$, (top panel) and the triangular, $v_3$, (bottom panel) flow coefficients of nonprompt D$^{0}$ mesons as functions of transverse momentum and in three bins of centrality. The bars and the boxes represent statistical and systematic uncertainties, respectively. The colored bands stand for theoretical predictions [37,38,39,40,41,42,43].

Summary

In summary, the elliptic ($v_2$) and triangular ($v_3$) flow harmonics of D$^{0}$ mesons that come from B hadron decay ($\mathrm{B} \rightarrow \mathrm{D}^{0}$) are measured in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV. The $v_2$ results suggest a transverse momentum dependence and a slight increase for less central collisions. A non-zero $v_3$ coefficient is observed with very weak centrality dependence. This implies that $b$ quark collectivity is affected by event-by-event fluctuations. The magnitudes of the flow coefficients are significantly lower for $\mathrm{B} \rightarrow \mathrm{D}^{0}$ than was measured for non-decay D$^{0}$ mesons. This magnitude difference is more pronounced in the case of $v_2$. Various theoretical calculations are also presented, showing qualitative agreement with data.

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