Measurement of the polarization of the $Î¥(1S)$ and $Î¥(2S)$ states in $p\bar{p}$ collisions at $\sqrt{s}=$1.96 TeV

Abstract

We present a study of the polarization of the $Υ(1S)$ and $Υ(2S)$ states using a $1.3 $ fb$^{-1}$ data sample collected by the D0 experiment in 2002--2006 during Run II of the Fermilab Tevatron Collider. We measure the polarization parameter $α=(σ_{T}-2σ_{L})/(σ_{T}+2σ_{L})$, where $σ_{T}$ and $σ_{L}$ are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum ($p_{T}^Υ$) for the $Υ(1S)$ and $Υ(2S)$. Significant $p_{T}^Υ$-dependent longitudinal polarization is observed for the $Υ(1S)$. A comparison with theoretical models is presented.

7 pages, 4 figures, 2 tables, submitted to Phys. Rev. Letters