Etude de la violation directe de CP dans la desintégration du meson b en mesons vecteurs incluant le mélange $\rho -\omega$ dans le cadre de l'expérience LHCb

$\rho^0-\omega$ mixing effect on direct CP violation in B decay into vector mesons is one of the main studies of this work. The first part is to the calculation of the decay amplitudes of the channels $B\to V \rho^0(\omega)$ wich have been modelized. We used for that the helicity formalism. In such a way branching ratios and asymmetries depending on form factor models and other parameters are predicted. Direct CP violation appears at several levels: in branching ratios, in angular distributions and in differential asymmetry as a function of $\rho^0-\omega$ mass. The dominance of the longitudinal polarization in the studied channels is confirmed by Babar and Belle experimental results. We calculated too the strong phase and the ratio of Penguin to Tree amplitudes for each modelized channel. In a second part, was developed an analysis of the channel $B^0 \to K^{*0}\rho^0(\omega)$ in the framework of LHCb experiment. It will start in 2007 and is to b flavor study and CP violation. The realistic analysis wich has been performed shows that this channel is not appropriated to observe $\rho^0-\omega$ mixing effect on asymmetry in LHCb, while the $\rho^+\rho^0(\omega)$ channel, for wich we have predicted a branching ratio value confirmed by Babar and Belle, is much more promising.