The B → D(*)lvl decays in the pQCD approach with the Lattice QCD input

Abstract

In this paper, we studied the semileptonic decays B→D(*)l−v¯l by using the “pQCD + Lattice QCD” method. We made the extrapolation for the six relevant form factors by using the input values obtained from the pQCD factorization approach in the low q2 region of 0≤q2≤mτ2 and the lattice QCD input at the endpoint q2=qmax2. We then calculated the ratios R(D) and R(D*) of the branching ratios ℬ(B→D(*)l−v¯l) and found numerically that (1) the “pQCD + Lattice QCD” predictions for the branching ratios ℬ(B→D(*)l−v¯l) agree well with the measured values within one standard deviation; and (2) the “pQCD + Lattice QCD” predictions for the ratios R(D(*)) are R(D)=0.337−0.037+0.038 and R(D*)=0.269−0.020+0.021; they agree with the data within 2σ deviation, in other words, one can explain the “R(D(*))-puzzle” in the framework of the Standard Model.