We propose a constituent quark model to evaluate heavy decay constants and form factors relevant for B → D ( * ) semileptonic transitions. We show that the model reproduces the scaling laws dictated by the spin-flavour symmetry in the heavy quark limit and describes quite well the experimental data.

By using a constituent quark model we compute the form factors relevant to semileptonic transitions of B mesons into low-lying p-wave charmed mesons. We evaluate the q 2 dependence of these form factors and compare them with other model calculations. The Isgur-Wise functions τ 1/2 and τ 3/2 are also obtained in the heavy quark limit of our results.

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