CMS-PAS-HIN-19-008

CMS-PAS-HIN-19-008
Search for strong electromagnetic fields in PbPb collisions at 5.02 TeV via azimuthal anisotropy of $\mathrm{D^0}$ and ${\mathrm{\overline{D}}{}^0}$ mesons
CMS Collaboration
November 2019

Abstract: Motivated by the search for strong electromagnetic fields created in PbPb collisions, the first measurement of the $v_2$ difference ( $\Delta v_2$ ) between $\mathrm{D^0}$ and ${\mathrm{\overline{D}}{}^0}$ is presented as a function of rapidity. The result for the rapidity-averaged $v_2$ difference is found to be $< \Delta v_2 > =$ 0.001 $\pm$ 0.001 (stat) $\pm$ 0.003 (syst), consistent with zero within experimental uncertainties. Comparisons with models may help to directly constrain the electric conductivity of the hot and dense medium formed in these collisions. Measurements of flow harmonics of $\mathrm{D^0}$ ( $\bar{u}c$ ) and ${\mathrm{\overline{D}}{}^0}$ ( $u\bar{c}$ ) mesons are presented as functions of rapidity ( $y$ ), transverse momentum ( $p_{\mathrm{T}}$ ), and collision centrality, for PbPb collisions at 5.02 TeV, using data collected by the CMS experiment during the 2018 LHC run. The results improve previous ones published by CMS, by extending the $p_{\mathrm{T}}$ coverage and providing more differential information. A clear centrality dependence of prompt $\mathrm{D^0}$ $v_2$ is observed, while $v_3$ is largely independent of centrality. The trend is consistent with expectations of flow driven by the initial-state geometry. No significant rapidity dependence of prompt ${\mathrm{\overline{D}}{}^0}$ $v_2$ and $v_3$ is observed.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 816 (2021) 136253. The superseded preliminary plots can be found here.

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