QCD improved top-quark decay at next-to-next-to-leading order

Abstract We analyse the top-quark decay at next-to-next-to-leading order (NNLO) in QCD by using Principle of Maximum Conformality (PMC) which provides a systematic way to eliminate renormalization scheme and scale ambiguities perturbative predictions. The PMC scales coupling constant $$\alpha _s$$ α s are determined absorbing non-conformal $$\beta $$ β terms that govern behavior running Renormalization Group Equation (RGE). obtain $$Q_\star =15.5$$ Q ⋆ = 15.5 GeV for decay, is an magnitude smaller than conventional choice $$\mu _r=m_t$$ μ r m t , reflecting small virtuality dynamics process. Moreover, due disappear pQCD series, there no renormalon divergence NLO correction term greatly increased while NNLO suppressed compared results obtained . By further including next-to-leading (NLO) electroweak corrections, finite W boson width bottom quark mass, we total $$\Gamma ^{\textrm{tot}}_t=1.3112^{+0.0190}_{-0.0189}$$ Γ tot 1 . 3112 - 0.0189 + 0.0190 GeV, where error squared averages mass $$\Delta m_t=\pm 0.7$$ Δ ± 0.7 \alpha _s(M_Z)=\pm 0.0009$$ ( M Z ) 0.0009 estimation unknown higher-order PAA method with [N/M]=[1/1]. improved predictions complementary previous calculations pair production helpful detailed studies properties top-quark.