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Next-to-leading-order QCD corrections to the yields and polarisations of J/Psi and Upsilon directly produced in association with a Z boson at the LHC
B. Gong, J. P. Lansberg1, C. Lorce1, 2, J. Wang

We update the study of the production of direct J/Psi in association with a Z boson at the Next-to-Leading Order (NLO) in alpha_s by evaluating both the yield differential in P_T and the J/Psi polarisation in the QCD-based Colour-Singlet Model (CSM). Contrary to an earlier claim, QCD corrections at small and mid P_T are small if one assumes that the factorisation and the renormalisation scales are commensurate with the Z boson mass. As it can be anticipated, the t-channel gluon-exchange (t-CGE) topologies start to be dominant only for P_T > mZ/2. The polarisation pattern is not altered by the QCD corrections. This is thus far the first quarkonium-production process where this is observed in the CSM. Along the same lines, our predictions for direct Upsilon+Z are also given.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
2 :  LPT - Laboratoire de Physique Théorique d'Orsay [Orsay]
Physique/Physique des Hautes Energies - Expérience

Physique/Physique des Hautes Energies - Phénoménologie
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