https://doi.org/10.1051/epjconf/20122804009
New Measurements of Upsilon Spin Alignment at the Tevatron
Department of Physics, Purdue University, USA
a e-mail: mjones@physics.purdue.edu
We describe a new analysis of γ(nS) → μ+μ− decays collected in 
collisions with the CDF II detector at the Fermilab Tevatron. This analysis measures the angular distributions of the final state muons in the γ rest frame, providing new information about γ production polarization. We find the angular distributions to be nearly isotropic up to γ pT of 40 GeV/c, consistent with previous measurements by CDF, but inconsistent with results obtained by the D0 experiment. The results are compared with recent NLO calculations based on color-singlet matrix elements and non-relativistic QCD with color-octet matrix elements.
© Owned by the authors, published by EDP Sciences, 2012
