Measurements of Quarkonium production and polarization at CMS

Studies of quarkonium production and polarization play an important role in understanding QCD. CMS has recently measured the $\Upsilon$(nS) (n=1,2,3) production cross sections and polarizations, as well as the prompt $\psi$(nS) (n=1,2) polarizations, using a dimuon sample collected in proton-proton collisions in 2011 at $\sqrt{s} =$ 7 TeV. The differential cross sections of the $\Upsilon$(nS) states are presented as a function of dimuon transverse momentum, covering a wide range of $p_\mathrm{T}$ (10--100 GeV). All three states show a similar behaviour and display a change of shape from an exponential to a power-law at $p_\mathrm{T} \approx$ 20 GeV. The polarizations of the $\Upsilon$(nS) and $\psi$(nS) states are determined in bins of dimuon transverse momentum and rapidity, significantly extending the $p_\mathrm{T}$ and rapidity ranges probed by previous experiments. The experimental measurements are in disagreement with current theoretical predictions.