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

Abstract

The polarizations of prompt and non-prompt J/psi and psi(2S) mesons are measured in proton-proton collisions at root s = 13TeV, 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(T), of the charmonium states, in the 25-120 and 20-100GeV ranges for the J/psi and psi(2S), respectively. The non-prompt polarizations agree with predictions based on the hypothesis that, for p(T) greater than or similar to 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(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 root s = 7TeV, the prompt polarizations show a significant variation with p(T), at low p(T).