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CMS-PAS-HIN-21-008
Measurements of the azimuthal anisotropy of charmonia in PbPb collisions at sNN= 5.02 TeV
Abstract: The second-order (v2) and third-order (v3) Fourier coefficients describing the azimuthal anisotropy of prompt and nonprompt J/ψ and prompt ψ(2S) mesons are measured in PbPb collisions at sNN= 5.02 TeV. The analysis uses a dataset corresponding to an integrated luminosity of 1.6 nb1 recorded with the CMS detector in 2018. J/ψ and ψ(2S) mesons are reconstructed using their dimuon decay channel. The v2 and v3 values are extracted using the scalar product method and studied as functions of meson transverse momentum and PbPb collision centrality. The measured v2 values for the prompt J/ψ mesons are larger than of those of nonprompt J/ψ mesons. The study of azimuthal anisotropy for prompt ψ(2S) mesons is reported for the first time, showing v2 larger than that of J/ψ mesons.
Figures & Tables Summary Additional Figures References CMS Publications
Figures

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Figure 1:
Invariant mass (left) and J/ψ (right) distributions for the bin of 3 <pT< 4.5 GeV/c and 0 <v2< 0.3 in centrality 10-60%. The solid lines represent the total fit while the dashed and dashed-dotted lines represent the prompt and nonprompt components, respectively. The background dimuons are described by the shaded boxes.

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Figure 1-a:
Invariant mass (left) and J/ψ (right) distributions for the bin of 3 <pT< 4.5 GeV/c and 0 <v2< 0.3 in centrality 10-60%. The solid lines represent the total fit while the dashed and dashed-dotted lines represent the prompt and nonprompt components, respectively. The background dimuons are described by the shaded boxes.

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Figure 1-b:
Invariant mass (left) and J/ψ (right) distributions for the bin of 3 <pT< 4.5 GeV/c and 0 <v2< 0.3 in centrality 10-60%. The solid lines represent the total fit while the dashed and dashed-dotted lines represent the prompt and nonprompt components, respectively. The background dimuons are described by the shaded boxes.

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Figure 2:
Simultaneous fits of the dimuon invariant mass spectrum and the v2S+B (left) and v3S+B (right) distributions for ψ(2S), as defined in Equation 4 for 6.5 <pT< 10 GeV/c and centrality 10-60%. In the top panel, the solid (signal + background) and dashed (background only) blue lines show the result of the mass fit. In the bottom panel, the vertical lines of the vsn points represent the statistical uncertainty. The solid (vn signal) and dashed (vn background) lines indicate the corresponding fit to the vn distributions.

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Figure 2-a:
Simultaneous fits of the dimuon invariant mass spectrum and the v2S+B (left) and v3S+B (right) distributions for ψ(2S), as defined in Equation 4 for 6.5 <pT< 10 GeV/c and centrality 10-60%. In the top panel, the solid (signal + background) and dashed (background only) blue lines show the result of the mass fit. In the bottom panel, the vertical lines of the vsn points represent the statistical uncertainty. The solid (vn signal) and dashed (vn background) lines indicate the corresponding fit to the vn distributions.

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Figure 2-b:
Simultaneous fits of the dimuon invariant mass spectrum and the v2S+B (left) and v3S+B (right) distributions for ψ(2S), as defined in Equation 4 for 6.5 <pT< 10 GeV/c and centrality 10-60%. In the top panel, the solid (signal + background) and dashed (background only) blue lines show the result of the mass fit. In the bottom panel, the vertical lines of the vsn points represent the statistical uncertainty. The solid (vn signal) and dashed (vn background) lines indicate the corresponding fit to the vn distributions.

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Figure 3:
v2 (top) and v3 (bottom) values as a function of pT (left panel) and collision centrality (right panel) for prompt and nonprompt J/ψ mesons. The results for pT 3-6.5 and 6.5-50 GeV/c are studied in the rapidity range of 1.6 <|y|< 2.4 and |y|< 2.4, respectively (left panel). The pT range for the right panel is pT 6.5-50 GeV/c and rapidity of |y|< 2.4. The vertical bars denote the statistical uncertainties, and the rectangular bands show the systematic uncertainties.

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Figure 4:
v2 (top) and v3 (bottom) values as a function of pT (left panel) and Npart (right panel) for prompt ψ(2S) mesons. The results for pT 4-6.5 and 6.5-50 GeV/c are studied in the rapidity range of 1.6 <|y|< 2.4 and |y|< 2.4, respectively (left panel). The pT range for the right panel is pT 6.5-50 GeV/c and rapidity of |y|< 2.4. The vertical bars denote the statistical uncertainties, and the rectangular bands show the systematic uncertainties.
Tables

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Table 1:
Summary of dominant systematic uncertainties
Summary
The second-order (v2) and third-order (v3) Fourier coefficients of the azimuthal distributions for prompt and nonprompt J/ψ mesons and prompt ψ(2S) mesons are measured in PbPb collisions as functions of pT and PbPb collision centrality. The v2 values for prompt and nonprompt J/ψ mesons both indicate a decreasing trend from mid-central towards central collision events. On the other hand, the v2 is found to be flat for pT> 9 GeV/c for prompt J/ψ mesons while the dependence on pT is found to be weak for nonprompt J/ψ mesons. The prompt J/ψ v2 values are found to be larger than that of nonprompt J/ψ throughout studied kinematic region, suggesting different in-medium effects for charm and beauty quarks. The observation of sizable and flattened v2 values at high-pT for prompt J/ψ mesons provides a hint of the contribution of jet quenching for prompt J/ψ suppression. The v3 values of prompt and nonprompt J/ψ are reported for the first time, where the results show consistency with zero in the measured pT and centrality intervals. Also, the v2 and v3 values for prompt ψ(2S) mesons are measured for the first time. The results show larger v2 values than J/ψ mesons in mid-pT region, indicating different degrees of recombination contribution for J/ψ and ψ(2S) mesons. The measured v3 values for both J/ψ and ψ(2S) are found to be consistent to zero within uncertainties in the overall kinematic range. These measurements provide a new insight in the understanding of the dynamics and in-medium effects of charmonia in heavy ion collisions.
Additional Figures

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Additional Figure 1:
v2 values for the prompt J/ψ mesons as a function of pT in the 10-60% centrality range measured at sNN= 5.02 TeV (blue circles) and sNN= 2.76 TeV (black squares) [20]. Both results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 2:
v2 values for the nonprompt J/ψ mesons as a function of pT in the 10-60% centrality range measured at sNN= 5.02 TeV (red diamonds) and sNN= 2.76 TeV (black squares) [20]. Both results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 3:
v2 values for the prompt J/ψ mesons measured with CMS (blue circles) and ATLAS (green squares) [19], and inclusive J/ψ mesons with ALICE (pink crosses) [21] as a function of pT at sNN= 5.02 TeV. CMS results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 4:
v2 values as a function of pT measured for nonprompt J/ψ mesons with CMS (red diamonds) and ATLAS (green squares) [19], and for bottom hadron decay muons (blue crosses) with ATLAS [43] at sNN= 5.02 TeV. CMS results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 5:
v3 values as a function of pT measured for prompt J/ψ mesons (blue circles) and prompt D0 mesons (green squares) [40] with CMS, for inclusive J/ψ mesons with ALICE (pink crosses) [21], and for charm hadron decay muons with ATLAS (brown triangles) [43] at sNN= 5.02 TeV. CMS results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 6:
v3 values as a function of pT measured for nonprompt J/ψ mesons (red diamonds) and nonprompt D0 mesons (green squares) [44] with CMS, and for bottom hadron decay muons with ATLAS (brown triangles) [43] at sNN= 5.02 TeV. CMS results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 7:
v2 values as a function of pT in the 10-60% centrality range for prompt J/ψ mesons (blue circles), nonprompt J/ψ mesons (red diamonds), prompt D0 mesons (green squares) [40], nonprompt D0 mesons (brown stars) [44], Υ(1S) mesons (purple crosses) [23], and charged hadrons (gray band) [45] measured with CMS at sNN= 5.02 TeV. J/ψ results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 8:
v2 values for the prompt J/ψ mesons (blue circles), nonprompt J/ψ mesons (red diamonds) and prompt ψ(2S) mesons (green squares) as a function of Npart for 6.5 <pT< 50 GeV/c. The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 9:
v2 values for the prompt J/ψ mesons (blue circles), nonprompt J/ψ mesons (red diamonds) and prompt ψ(2S) (green squares) as a function of pT in the 10-60% centrality range. All three results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 10:
v3 values for the prompt J/ψ mesons (blue circles), nonprompt J/ψ mesons (red diamonds) and prompt ψ(2S) mesons (green squares) as a function of Npart for 6.5 <pT< 50 GeV/c. The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 11:
v3 values for the prompt J/ψ mesons (blue circles), nonprompt J/ψ mesons (red diamonds) and prompt ψ(2S) mesons (green squares) as a function of pT in the 10-60% centrality range. All three results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 12:
v2 (top) and v3 (bottom) values of prompt J/ψ mesons (blue circles) and prompt ψ(2S) mesons (green squares) as functions of pT (left) and Npart. Both results are shown in rapidity 1.6 <|y|< 2.4 (open markers) and |y|< 2.4 (closed markers). The error bars and boxes represent the statistical and systematic uncertainties, respectively.

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Additional Figure 13:
The v2 values of J/ψ mesons (blue circles) as a function of pT in the 10-60% centrality range compared with a theoretical calculation using leading power NRQCD and LBT model [46] (green dashed line). The results for 3 <pT< 6.5 and 6.5 <pT< 50 GeVc are studied in the rapidity range of 1.6 <|y|< 2.4 and |y|< 2.4, respectively. The vertical bars denote the statistical uncertainties, and the rectangular bands show the systematic uncertainties.
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Compact Muon Solenoid
LHC, CERN