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

Abstract

In this paper, we analyze the top-quark decay t→Wb up to next-to-next-to-next-to-leading order (N3LO) 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 N4LO terms. In our calculation, an effective strong coupling constant αs(Q*) is determined by using all nonconformal {βi} 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., Γttot=1.3120±0.0038  GeV, whose error is the squared average of the uncertainties from the decay width of W-boson ΔΓW=±0.042  GeV, the coupling constant Δαs(mZ)=±0.0009, and the predicted N4LO-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., Δmt=±0.7  GeV, we obtain Γttot=1.3120−0.0192+0.0194  GeV. Published by the American Physical Society 2024