Improved analysis of the decay width of t → Wb up to N3LO QCD corrections

In this paper, we analyze the top-quark decay t -> Wb up to next-to-next-to-next-to-leading order ((NLO)-L-3) QCD corrections. For the purpose, we first adopt the principle of maximum conformality (PMC) to deal with the initial perturbative QCD (pQCD) series. Then we adopt the Bayesian analysis approach, which quantifies the unknown higher-order terms' contributions in terms of a probability distribution, to estimate the possible magnitude of the uncalculated (NLO)-L-4 terms. In our calculation, an effective strong coupling constant alpha(a)(Q(*)) is determined by using all nonconformal {beta(i)} terms associated with the renormalization group equation. This leads to a next-to-leading-log PMC scale Q(*)((NLL)) 10.3048 GeV, which can be regarded as the correct momentum flow of the process. Consequently, we obtain an improved scale-invariant pQCD prediction for the top-quark decay width, e.g., Gamma(tot)(t) = 1.3120 +/- 0.0038 GeV, whose error is the squared average of the uncertainties from the decay width of W-boson Delta Gamma(W) = +/- 0.042 GeV, the coupling constant Delta alpha(a)(m(Z)) = +/- 0.0009, and the predicted (NLO)-L-4-terms. The magnitude of the top-quark pole mass greatly affects the total decay width. By further taking the PDG top-quark pole mass error from cross-section measurements into consideration, e.g., Delta m(t) = +/- 0.7 GeV, we obtain Gamma(tot)(t) = 1.3120(-0.0192)(+0.0194) GeV.