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

The polarizations of prompt and non-prompt J∕ψ and ψ(2S) mesons are measured in proton-proton collisions
at √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, 𝜆𝜗, is measured as a function of the transverse momentum, 𝑝$_T$, of the
charmonium states, in the 25–120 and 20–100 GeV ranges for the J∕ψ and ψ(2S), respectively. The non-prompt
polarizations agree with predictions based on the hypothesis that, for 𝑝T ≳ 25 GeV, the non-prompt J∕ψ and ψ(2S)
are predominantly produced in two-body B meson decays. The prompt results clearly exclude strong transverse
polarizations, even for 𝑝$_T$ exceeding 30 times the J∕ψ mass, where 𝜆𝜗 tends to an asymptotic value around 0.3.
Taken together with previous measurements, by CMS and LHCb at √𝑠 = 7 TeV, the prompt polarizations show a
significant variation with 𝑝$_T$, at low 𝑝$_T$.