Etudes des désintégrations de mésons beaux avec photons convertis dans l'expérience $LHC_b$

The LHCb experiment studies CP violation in B meson decays and will take data in 2007. Analysis strategy are studied on simulations. In this development, I worked on many fields, and essentially in: - converted photons reconstruction: the charge deposited by electrons and positrons produced by converted photons can be seen and allow to detect them. The low rate of conversion is of course to consider and the use of converted photons is advantageous only because of their good momentum measurements. - decay channels with converted photon selection: the good momentum resolution allows to select different channels, among which: B0 -> K* gamma, B0 -> pi- pi+ pi0 and B0 -> pi0 pi0. Despite low branching ratios, I show that these modes can be studied. The classical method with photons detected by the electromagnetical calorimeter being difficult, the use of converted photons will be an advantage for LHCb.