Measurements of Quarkonium Production and Polarization at CMS

Abstract

The polarizations of Y(nS) (n=1,2,3) and prompt J/\psi and \psi(2S), as well as the differential cross section of the Y(nS), are measured in proton-proton collisions at sqrt(s) = 7 TeV, using a dimuon data sample collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 4.9 fb-1. The differential cross section is measured as a function of transverse momentum of Y(nS). The data show a transition from exponential to power-law behavior in the neighborhood of 20 GeV, and the power-law exponents for all three states are consistent. The polarization parameters \lambda\theta, \lambda\phi, and \lambda\theta\phi, as well as the frame-invariant quantity \lambda, are measured from the dimuon decay angular distributions in three different polarization frames. No evidence of large polarizations is seen in these kinematic regions, which extend much beyond those previously explored.