Measurement of the polarizations of prompt and non-prompt and ψ(2S) mesons produced in pp collisions at s=13TeV

Abstract

The polarizations of prompt and non-prompt

and $\psi \left(\mathrm{2S}\right)$ 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${\text{fb}}^{-1}$. Based on the analysis of the dimuon decay angular distributions in the helicity frame, the polar anisotropy, ${\lambda }_{\vartheta }$, 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

and $\psi \left(\mathrm{2S}\right)$, respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for $p_T\gtrsim 25\text{GeV}$, the non-prompt

and $\psi \left(\mathrm{2S}\right)$ 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

mass, where ${\lambda }_{\vartheta }$ 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 $p_T$, at low $p_T$.