Semileptonic decays B→D~(*) lυ 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 R_D~( 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 R_D~1 and R_D~s ratios,the pQCD predictions are R_D~l=0.450-0.051+0.064 and R_D~s=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.