Measurements of the Angular Distributions of Muons from Υ Decays in pp̅ Collisions at √s=1.96 TeV

Abstract

The angular distributions of muons from Υ(1S,2S,3S)→μ+μ- decays are measured using data from pp̅ collisions at √s=1.96 TeV corresponding to an integrated luminosity of 6.7 fb-1 and collected with the CDF II detector at the Fermilab Tevatron. This analysis is the first to report the full angular distributions as functions of transverse momentum pT for Υ mesons in both the Collins-Soper and s-channel helicity frames. This is also the first measurement of the spin alignment of Υ(3S) mesons. Within the kinematic range of Υ rapidity |y|<0.6 and pT up to 40 GeV/c, the angular distributions are found to be nearly isotropic.