Measurement of the Υ(1S), ϒ(2S), and ϒ(3S) Polarizations in pp Collisions at √s = 7 TeV

The polarizations of the Υ(1S), ϒ(2S), and ϒ(3S) mesons are measured in proton-proton collisions at √s = 7 TeV, using a data sample of ϒ(nS) → μ⁺μ^- decays collected by the CMS experiment, corresponding to an integrated luminosity of 4.9 fb^-1. The dimuon decay angular distributions are analyzed in three different polarization frames. The polarization parameters λ_ν, λ_φ, and λ_νφ, as well as the frame-invariant quantity λ^~, are presented as a function of the ϒ(nS) transverse momentum between 10 and 50 GeV, in the rapidity ranges |y| < 0.6 and 0.6 < |y| < 1.2. No evidence of large transverse or longitudinal polarizations is seen in the explored kinematic region.