HQEFT as a Large Component QCD and Comments on the Incompleteness of HQET

The heavy quark effective field theory (HQEFT) is revisited in a more intuitive way. It is shown that HQEFT is a consistent large component QCD of heavy quarks. In the nonrelativistic limit, HQEFT recovers the nonrelativistic QCD (NRQCD). The resulting new effects in the HQEFT of QCD are carefully re-examined. It is then natural to give comments on the usual heavy quark effective theory (HQET). Consistent phenomenological applications of HQEFT exhibit its interesting features and completeness in comparison with HQET. It then becomes manifest why we shall base on the HQEFT of QCD rather than HQET which is incomplete for computing 1/mQ corrections. More precise extraction for ∣Vcb∣ and ∣Vub∣ in the HQEFT of QCD is emphasized.