中文摘要：

In this paper, we studied the semileptonic decays B→D（*）l-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 p QCD factorization approach in the low q2 region of 0≤q2≤mt2 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-l )and found numerically that（1） the ‘‘pQCD+ Lattice QCD’’ predictions for the branching ratios B(B→D（*）l-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）=0:3370.0370.038and R（D*）=0:2690.0200.021 ; they agree with the data within 2δ deviation, in other words, one can explain the ‘‘R（D）-puzzle’’ in the framework of the Standard Model.

英文摘要：

In this decays B → D^（＊）l^-vl paper, we studied by using the the semileptonic ＂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 ≤ q^2≤≤mt^2 and the lattice QCD input at the endpoint q^2 = q^2max· We then calculated the ratios R（D） and R（D^＊） of the branching ratios B（B→ D^（＊）l^-vl） and found numeri- cally that （1） the ＂pQCD ＋ Lattice QCD＂ predictions for the branching ratios B（B → D^（＊）l^-vl） 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） =0.037-0.037^＋0.038 and R（D^＊） = 20269-03020^＋03021;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.