Revisiting the top-quark pair production at future e+e- colliders

In this study,we reanalyze the top-quark pair production at next-to-next-to-leading order (NNLO) in quantum chromodynamics (QCD) at future e+e-colliders using the Principle of Maximum Conformality (PMC)method.The PMC renormalization scales in αsare determined by absorbing the non-conformal β terms by recursively using the Renormalization Group Equation (RGE).Unlike the conventional scale-setting method of fixing thescale at the center-of-mass energy ■,the determined PMC scale ■ is far smaller than the ■ and increases with the ■,yielding the correct physical behavior for the top-quark pair production process.Moreover,the convergence of the pQCD series for the top-quark pair production is greatly improved owing to the elimination of therenormalon divergence.For a typical collision energy of■GeV,the PMC scale is■GeV;the QCDcorrection factor K for conventional results is ■,where the first error is caused by varying the scale ■ and the second error is from the top-quark mass ?mt=±0.7GeV.After applying the PMC,the renormalization scale uncertainty is eliminated,and the QCD correction factor K is improved to ■,where the error is from the top-quark mass ?mt=±0.7GeV.The PMC improved predictions for the top-quark pair production are helpful for detailed studies of the properties of the top-quark at future e+e-colliders.