Measurement of the polarization of the upsilon(1S) and upsilon(2S) states in p(p)over-bar Collisions at root s=1.96 TeV

We present a study of the polarization of the upsilon(1S) and upsilon(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 alpha=(sigma(T)-2 sigma(L))/(sigma(T)+2 sigma(L)), where sigma(T) and sigma(L) are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (p(T)(upsilon)) for the upsilon(1S) and upsilon(2S). Significant p(T)(upsilon)-dependent longitudinal polarization is observed for the upsilon(1S). A comparison with theoretical models is presented.