Application of the Principle of Maximum Conformality to Top-Pair Production

الأصل · EN

A major contribution to the uncertainty of finite-order perturbative QCD predictions is the perceived ambiguity in setting the renormalization scale μᵣ. For example, by using the conventional way of setting μᵣ ∈ [mₜ/2,2mₜ], one obtains the total t t production cross-section σt t with the uncertainty Δσt t/σt t (⁺³%₋₄%) at the Tevatron and LHC even for the present NNLO level. The Principle of Maximum Conformality (PMC) eliminates the renormalization scale ambiguity in precision tests of Abelian QED and non-Abelian QCD theories. In this paper we apply PMC scale-setting to predict the t t cross-section σtt at the Tevatron and LHC colliders. It is found that σtt remains almost unchanged by varying μ initᵣ within the region of [mₜ/4,4mₜ]. The convergence of the expansion series is greatly improved. For the (qq)-channel, which is dominant at the Tevatron, its NLO PMC scale is much smaller than the top-quark mass in the small x-region, and thus its NLO cross-section is increased by about a factor of two. In the case of the (gg)-channel, which is dominant at the LHC, its NLO PMC scale slightly increases with the subprocess collision energy √s, but it is still smaller than mₜ for √s 1 TeV, and the resulting NLO cross-section is increased by 20%. As a result, a larger σtt is obtained in comparison to the conventional scale-setting method, which agrees well with the present Tevatron and LHC data. More explicitly, by setting mₜ=172.9± 1.1 GeV, we predict σ Tevatron,1.96TeV = 7.626⁺⁰.²⁶⁵₋₀.₂₅₇ pb, σ LHC,7TeV = 171.8⁺⁵.⁸₋₅.₆ pb and σ LHC,14TeV = 941.3⁺²⁸.⁴₋₂₆.₅ pb. [full abstract can be found in the paper.]