Measurement of the decayB→Dℓνℓin fully reconstructed events and determination of the Cabibbo-Kobayashi-Maskawa matrix element

Abstract

We present a determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element |V cb | using the decay B → D ν ( = e, µ) based on 711 fb −1 of e + e − → Υ(4S) data recorded by the Belle detector and containing 772 × 10 6 BB pairs. One B meson in the event is fully reconstructed in a hadronic decay mode while the other, on the signal side, is partially reconstructed from a charged lepton and either a D + or D 0 meson in a total of 23 hadronic decay modes. The isospinaveraged branching fraction of the decay B → D ν is found to be B(B 0 → D − + ν ) = (2.31 ± 0.03(stat) ± 0.11(syst))%. Analyzing the differential decay rate as a function of the hadronic recoil with the parameterization of Caprini, Lellouch and Neubert and using the form-factor prediction G(1) = 1.0541 ± 0.0083 calculated by FNAL/MILC, we obtain ηEW|V cb | = (40.12 ± 1.34) × 10 −3 , where ηEW is the electroweak correction factor. Alternatively, assuming the model-independent form-factor parameterization of Boyd, Grinstein and Lebed and using lattice QCD data from the FNAL/MILC and HPQCD collaborations, we find ηEW|V cb | = (41.10 ± 1.14) × 10 −3 .

Perturbative corrections to B → D form factors in QCD

“…in tables 2 and 3 with selections of the q 2 bins identical to that from the Belle and BaBar measurements [71,72]. In particular, our predictions for the total decay width of B → Dµν µ in units of 1/|V cb | 2 can be obtained straightforwardly with the recent experimental measurements of the total branching fraction from the Belle [71] and BaBar [73] Collaborations.…”

“…the recent experimental measurements from Belle [71] and BaBar [73] led to the extracted values of |V cb | at O(10%) accuracy as displayed in (5.19). Our predictions for the B → D form factors also gave rise to the determinations of R(D) presented in (5.21), confronted with the HFAG average value in [2].…”

“…In particular, our predictions for the total decay width of B → Dµν µ in units of 1/|V cb | 2 can be obtained straightforwardly with the recent experimental measurements of the total branching fraction from the Belle [71] and BaBar [73] Collaborations. 2 The resulting determinations of |V cb | suffer from a sizeable uncertainty, approximately O(10%), due to the LCSR calculations of B → D form factors at large hadronic recoil.…”

“…[ 0.02 ± 0.01 Table 2. Theory predictions for the partial decay rates of B → Dµν µ compared with the Belle measurements from [71].…”

“…The differential q 2 distributions for B → D ν obtained with the form factors f +,0 BD (q 2 ) displayed in table 1 are plotted in figure 8, including also the recent experimental measurements for the combination of B + →D 0 e + ν e , B 0 → D − e + ν e , B + →D 0 µ + ν µ and B 0 → D − µ + ν µ from the Belle Collaboration [71]. It is evident that our predictions for the q 2 shape of B → Dµν µ are in excellent agreement with the experimental data bins.…”