WEAK DECAY PROCESS OF B-]PL(V)OVER-BAR(L) - A VARYING EXTERNAL-FIELD APPROACH IN QCD SUM-RULES

A varying external field approach in QCD sum rules is formulated in a systematic way to treat the weak decay form factors and their q(2) dep endence in the process of B-->rho l<(nu)over bar>(1). From the form fa ctor sum rules, we can also obtain the mass sum rules for B and rho me sons, which can help us determine the reliable Borel windows in studyi ng the relevant form factor sum rules. In this way, we thus demonstrat e that some QCD sum rule calculations in the literature are less relia ble. We also include induced condensate contributions, which have been ignored, into the relevant sum rules. We obtain the ratios Gamma((B) over bar(0)-->rho(+)e(-)<(nu)over bar>(e))/Gamma((B) over bar(0)-->pi( +)e(-)<(nu)over bar>(e)) approximate to 0.94 and Gamma((B) over bar(0) -->rho(+)tau(-)<(nu)over bar>(tau))/Gamma((B) over bar(0)-->pi(+)tau(- )<(nu)over bar>(tau))approximate to 1.15. We apply this approach to re examine the case of the D meson decay.