Observation of Polarization in Bottomonium Production at sqrt(s)=38.8   GeV
  We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at sqrt(s)=38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state show no polarization at small xF and pT but significant positive transverse production polarization for either pT > 1.8 GeV/c or for xF > 0.35. The Upsilon(2S+3S) unresolved states show a large transverse production polarization at all values of xF and pT measured. These observations are compared with an NRQCD calculation that predicts a transverse polarization in bottomonium production arising from quark-antiquark fusion and gluon-gluon fusion diagrams. 
C. N. Brown, T. C. Awes, M. E. Beddo, M. L. Brooks, J. D. Bush, T. A.   Carey, T. H. Chang, W. E. Cooper, C. A. Gagliardi, G...