New determination of |Vcb| using the three-loop QCD corrections for the B → D* semi-leptonic decays

We present a new determination of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| by using the three-loop perturbative QCD corrections for the B & RARR; D* semi-leptonic decay. The decay width of B & RARR; D* semi-leptonic decay can be factorized as perturbatively calculable short-distance part and the non-perturbative but universal long-distance part. We adopt the principle of maximum conformality (PMC) single-scale setting approach to deal with the perturbative series so as to achieve a precise fixed-order prediction for the short-distance parameter & eta;A. By applying the PMC, an overall effective & alpha;s value is achieved by recursively using the renormalization group equation, which inversely results in a precise scale-invariant pQCD series. Such scale-invariant series also provides a reliable basis for predicting the contributions from uncalculated perturbative terms. We then obtain & eta;A = 0.9225+0.0117 -0.0168, where the error is the squared average of those from & alpha;s(MZ) = & PLUSMN;0.0010 and the uncertainties caused by the uncalculated higher-order perturbative terms. By using the data of B & RARR; D*& nu; over bar , we finally obtain |Vcb|PMC = (40.60+0.53 which is consistent with the PDG value within errors.& COPY; 2022 Elsevier B.V. All rights reserved.