Measurements of the angular distributions of muons from Y decays in pp̄ 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 pp̄ collisions at √s=1.96TeV corresponding to an integrated luminosity of 6.7fb -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 p T 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 p T up to 40GeV/c, the angular distributions are found to be nearly isotropic. © 2012 American Physical Society.