HEAVY-QUARK LIMIT IN THE LIGHT-FRONT QUARK-MODEL

An explicit relativistic light-front quark model is presented which gi ves the momentum transfer dependent form factors of weak hadronic curr ents among heavy pseudoscalar and vector mesons in the whole accessibl e kinematical region 0 less than or equal to q(2) less than or equal t o q(max)(2). It is shown that in the limit of infinite masses of activ e quarks these form factors can be expressed in terms of universal Isg ur- Wise function. The explisit expression for this function is obtain ed. It is shown that neglect of pair creation from the vacuum in calcu lations of form factors does not violate Luke's theorem.