Polarization in Quarkonium Production
Abstract
Production mechanisms for quarkonium states in hadronic collisions remain difficult to understand. The decay angular distributions of J/ or (nS) states into μ+ μ- final states are sensitive to the matrix elements in the production process and provide a unique tool to evaluate different models. This talk will focus on new results for the spin alignment of (nS) states produced in pp collisions at s = 1.96 TeV using the CDF II detector at the Fermilab Tevatron. The data sample corresponds to an integrated luminosity of 6.7 fb-1. The angular distributions are analyzed as functions of the transverse momentum of the dimuon final state in both the Collins-Soper and the s-channel helicity frames using a unique data-driven background determination method. Consistency of the analysis is checked by comparing frame-invariant quantities derived from parametrizations of the angular distributions measured in each choice of reference frame. This analysis is the first to quantify the complete three-dimensional angular distribution of (1S), (2S) and (3S) decays. The decays are nearly isotropic in all frames, even when produced with large transverse momentum.