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 non-relativistic limit, HQEFT recovers the non-relativistic QCD (NRQCD). The resulting new effects in the HQEFT of QCD are carefully reexamined. It is then natural to come to the 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 an incomplete one for computing 1/m_Q corrections. More precise extraction for |V_{cb}| and |V_{ub}| in the HQEFT of QCD is emphasized.