ϒ(nS) Polarization in pp Collisions at the LHC with the CMS Experiment

The polarizations of the ϒ(1S), ϒ(2S) and ϒ(3S) mesons produced in proton-proton collisions at s=7TeV are measured using a data sample collected with the CMS detector in 2011. The data correspond to an integrated luminosity of 4.9fb−1. The measurements are based on the analysis of the dimuon decay angular distributions, analyzed in three different polarization frames, and are presented as a function of the ϒ transverse momentum in two rapidity ranges. The measurement of the polarization parameters, λθ,λϕ and λθϕ, is complemented by the determination of the frame-invariant quantity λ¯, which provides a useful intrinsic test of the reliability of the whole analysis chain as well as supplementary physical information. The polarizations of the three ϒ states are found to be small in the considered kinematic region (10