Measurement of the polarizations of prompt and non-prompt J/$\psi$ and $\psi$(2S) mesons produced in pp collisions at $\sqrt{s}$ = 13 TeV

Abstract

The polarizations of prompt and non-prompt J$/\psi$ and $\psi$(2S) mesons are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV, using data samples collected by the CMS experiment in 2017 and 2018, corresponding to a total integrated luminosity of 103.3 fb${}^{-1}$. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, ${\lambda }_{\theta }$, is measured as a function of the transverse momentum, $p_{\mathrm{T}}$, of the charmonium states, in the 25-120 and 20-100 GeV ranges for the J$/\psi$ and $\psi$(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for $p_{\mathrm{T}}$ $\gtrsim$ 25 GeV, the non-prompt J$/\psi$ and $\psi$(2S) are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse polarizations, even for $p_{\mathrm{T}}$ exceeding 30 times the J$/\psi$ mass, where ${\lambda }_{\theta }$ tends to an asymptotic value around 0.3. Taken together with previous measurements, by CMS and LHCb at $\sqrt{s}$ = 7 TeV, the prompt polarizations show a significant variation with $p_{\mathrm{T}}$, at low $p_{\mathrm{T}}$.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-22-009 (CMS Public Pages)

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