Semileptonic decays $B\to (\pi ,\rho )e\nu$ in relativistic quark model

Abstract

Quark model results for the $B\to \pi ,\rho$ decays are analysed, making use of the dispersion formulation of the model: The form factors at $q^2>0$ are expressed as relativistic invariant double spectral representation over invariant masses of the initial and final mesons through their light--cone wave functions. The dependence of the results on the quark model parameters is studied. For various versions of the quark model the ranges $\Gamma ({\bar{B}}^0\to {\pi }^{+}e\bar{\nu })=(7\pm 2)\times 10^{12}|V_{ub}{|}^2{s}^{-1}$, $\Gamma ({\bar{B}}^0\to {\rho }^{+}e\bar{\nu })/\Gamma ({\bar{B}}^0\to {\pi }^{+}e\bar{\nu })=1.45\pm 0.1$, and ${\Gamma }_L/{\Gamma }_T=0.7\pm 0.08$ are found. The effects of the constituent quark transition form factor are briefly discussed.

Comments: latex, 8 pages, 2 figures