Energy dependence of direct-quarkonium production in pppp collisions from fixed-target to LHC energies: complete one-loop analysis

Abstract : We compute the energy dependence of the P_T-integrated cross section of directly produced quarkonia in pp collisions at next-to-leading order (NLO), namely up to alpha_s^3, within nonrelativistic QCD (NRQCD). Our analysis is based on the idea that the P_T-integrated and the P_T-differential cross sections can be treated as two different observables. The colour-octet NRQCD parameters needed to predict the P_T-integrated yield can thus be extracted from the fits of the P_T-differential cross sections at mid and large P_T. For the first time, the total cross section is evaluated in NRQCD at full NLO accuracy using the recent NLO fits of the P_T-differential yields at RHIC, the Tevatron and the LHC. Both the normalisation and the energy dependence of the J/psi, psi' and Upsilon(1S), we obtained, are in disagreement with the data irrespective of the fit method. The same is true if one uses CEM-like colour-octet NRQCD parameters. If, on the contrary, one disregards the colour-octet contribution, the existing data in the TeV range are well described by the alpha_s^3 contribution in the colour-singlet model --which, at alpha_s^4, however shows an unphysical energy dependence. A similar observation is made for eta(c,b). This calls for a full NNLO or for a resummation of the initial-state radiation in this channel. In any case, past claims that colour-octet transitions are dominantly responsible for low-P_T quarkonium production are not supported by our results. This may impact the interpretation of quarkonium suppression in high-energy proton-nucleus and nucleus-nucleus collisions.
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http://hal.in2p3.fr/in2p3-01157184
Contributeur : Sophie Heurteau <>
Soumis le : mercredi 27 mai 2015 - 17:19:47
Dernière modification le : jeudi 11 janvier 2018 - 06:12:40

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Y. Feng, J. P. Lansberg, J.-X. Wang. Energy dependence of direct-quarkonium production in pppp collisions from fixed-target to LHC energies: complete one-loop analysis. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2015, 75 (7), pp.313. 〈10.1140/epjc/s10052-015-3527-1〉. 〈in2p3-01157184〉

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