Next-to-leading-order QCD correction to inclusive J/{psi}({Upsilon}) production in Z{sup 0} decay

Journal Article · Wed Sep 01 04:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.82.054006· OSTI ID:21432959

Li, Rong; Wang, Jian-Xiong ^[1]

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1. Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918(4), Beijing, 100049, China, and Theoretical Physics Center for Science Facilities, CAS, Beijing, 100049 (China)

In this paper, we study the J/{psi}({Upsilon}) production in Z boson decay in a color-singlet model (CSM). We calculate the next-to-leading-order (NLO) QCD correction to Z{yields}quarkonium+QQ, the dominant contribution in the CSM, with the vector and axial-vector parts in the ZQQ vertex being treated separately. The results show that the vector and axial-vector parts have the same K factor (the ratio of the NLO result to the leading-order result) 1.13 with the renormalization scale {mu}=2m{sub c} and m{sub c}=1.5 GeV, and the K factor falls to 0.918 when applying the Brodsky, Lepage, and Mackenzie (BLM) renormalization scale scheme with obtained {mu}{sub BLM}=2.28 GeV and m{sub c}=1.5 GeV. By including the contributions from the next-dominant ones, the photon and gluon fragmentation processes, the branching ratio for Z{yields}J/{psi}{sub prompt}+X is (7.3-10.0)x10{sup -5} with the uncertainty consideration for the renormalization scale and charm quark mass. The results are about one-half of the central value of the experimental measurement 2.1x10{sup -4}. Furthermore, the J/{psi} energy distribution in our calculation cannot describe the experimental data. Therefore, even at QCD NLO, the contribution to Z{yields}J/{psi}{sub prompt}+X from the CSM cannot fully account for the experimental measurement. And there should be contributions from other mechanisms, such as the color-octet (COM) contributions. We define R{sub cc}=({Gamma}(Z{yields}J/{psi}ccX)/{Gamma}(Z{yields}J/{psi}X)) and obtain R{sub cc}=0.84 for only the CSM contribution and R{sub cc}=0.49 for COM and CSM contributions together. Then the R{sub cc} measurement could be used to clarify the COM contributions.

• OSTI ID: 21432959
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 5 Vol. 82; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

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