A more precise extraction of |V-cb| in HQEFT of QCD

The more precise extraction for the CKM matrix element |Vcb| in the heavy quark effective field theory (HQEFT) of QCD is studied from both exclusive and inclusive semileptonic B decays. The values of relevant nonperturbative parameters up to order $1/m^2_Q$ are estimated consistently in HQEFT of QCD. Using the most recent experimental data for B decay rates, |Vcb| is updated to be |Vcb|=0.0395±0.0011expt±0.0019theor from B→D*lν decay and |Vcb|=0.0434±0.0041expt±0.0020theor from B→Dlν decay as well as |Vcb|=0.0394±0.0010expt±0.0014theor from inclusive B→Xclν decay.