Subleading form factors at order 1/m{sub Q} in terms of leading quantities using the nonforward amplitude in heavy quark effective theory

We consider the nonforward amplitude within the heavy quark effective theory. We show that one can obtain new information on the subleading corrections in 1/m{sub Q}. We illustrate the method by deriving new simple relations between the functions {xi}{sub 3}(w) and {lambda}{xi}(w) and the sums {sigma}{sub n}{delta}E{sub j}{sup (n)}{tau}{sub j}{sup (n)}(1){tau}{sub j}{sup (n)}(w) (j=(1/2),(3/2)), that involve leading quantities, namely, the Isgur-Wise functions {tau}{sub j}{sup (n)}(w) and the level spacings {delta}E{sub j}{sup (n)}. Our results follow because the nonforward amplitude B(v{sub i}){yields}D{sup (n)}(v{sup '}){yields}B(v{sub f}) depends on three variables (w{sub i},w{sub f},w{sub if})=(v{sub i}{center_dot}v{sup '},v{sub f}{center_dot}v{sup '},v{sub i}{center_dot}v{sub f}) independent in a certain domain, and we consider the zero recoil frontier (w,1,w) where only a finite number of j{sup P} states contribute ((1/2){sup +},(3/2){sup +}). These sum rules reduce to known results at w=1, for {lambda} obtained by Voloshin, and for {xi}{sub 3}(1) obtained by Le Yaouanc et al. and by Uraltsev, and generalizes them to all values of w. We discuss phenomenological applications of these results, in particular the check of Bakamjian-Thomas quarks models and the comparison with the QCD sum rules approach.