CMS-PAS-HIN-19-002

CMS-PAS-HIN-19-002
Measurement of the elliptic flow of $\Upsilon\textrm{(1S)}$ and $\Upsilon\textrm{(2S)}$ mesons in PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV
CMS Collaboration
November 2019

Abstract: The second-order Fourier coefficients ( $v_{2}$ ) characterizing the azimuthal dependence of $\Upsilon\textrm{(1S)}$ and $\Upsilon\textrm{(2S)}$ mesons arising from PbPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 5.02 TeV are determined. The $\Upsilon$ mesons are reconstructed using the di-muon decay channel as measured using the CMS detector. The dataset was obtained in 2018 and corresponds to an integrated luminosity of 1.7 nb $^{-1}$ . The scalar product method is used for the $v_{2}$ analysis. Results are reported for the rapidity range $\|y\| <$ 2.4, with 0 $< p_{\mathrm{T}} <$ 50 GeV, and in four centrality classes of 0-10%, 10-30%, 30-50% and 50-90%, with 0-10% corresponding to the most central collisions. The average $v_{2}$ value for $\Upsilon\textrm{(1S)}$ mesons is 0.007 $\pm$ 0.011 (stat) $\pm$ 0.005 (syst) in the 10-90% centrality interval. The observed $v_{2}$ values are consistent with zero for all $p_{\mathrm{T}}$ and centrality ranges, with a maximum offset of 2.5 standard deviations. The $v_{2}$ value for $\Upsilon\textrm{(2S)}$ mesons is measured for the first time and found to be -0.063 $\pm$ 0.085 (stat) $\pm$ 0.037 (syst) in the 10-90% centrality interval.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 819 (2021) 136385. The superseded preliminary plots can be found here.

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