Semileptonic decays B → D（＊） lv in the perturbative QCD factorization approach

In this paper,we study the B→D* l-l -ι semileptonic decays and calculate the branching ratios B(B→D* l-l -ι) and the ratios R(D*) and RD l,s by employing the perturbative QCD（pQCD）factorization approach.We find that（a）for R（D）and R（D*）ratios,the pQCD predictions are R（D）=0.430-0.026?0.021,R（D*）=0.301±0.013 and agree well with BaBar’s measurements of ReD e?T T;（b）for the newly defined RD1 and RDs ratios,the pQCD predictions are RDl=0.450-0.051+0.064 and RDs=0.642-0.070+0.081,which may be more sensitive to the QCD dynamics of the considered semileptonic decays than R(D*) and should be tested by experimental measurements.