Measurement of the polarization of the upsilon(1S) and upsilon(2S) states in pp collisions at square root[s]=1.96 TeV.

Joint Institute for Nuclear Research, Dubna, Russia.
Physical Review Letters (Impact Factor: 7.51). 11/2008; 101(18):182004.
Source: PubMed


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}-2sigma_{L})/(sigma_{T}+2sigma_{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.

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