Model independent determination of |Vub| in heavy meson effective thoery

We propose a strategy of the model-independent determination of the Kobayashi-Maskawa matrix element $|V_{ub}|$ within the framework of the heavy meson effective theory. The effective theory is model-independent, since no assumption on the dynamics is introduced except for the symmetry of QCD. Although the effective theory can only be applied to the decay process with soft pions, high detection efficiency on the soft pions in the future B-factories makes this theory effective. The two exclusive processes, $B \rightarrow \pi l \nu$ and $B \rightarrow \pi \pi l \nu$, are used to determine the value of $|V_{ub}|$, under the condition that the values of the decay constants of $B$ and $B^*$ mesons are given.