Rare decays in BaBar: Search for neutral B meson going to lepton-antilepton decays and measurement of CP asymmetry in inclusive B meson going to X(s) meson-gamma decays

Abstract

The purpose of this thesis is the study of rare decays with the BABAR detector. In the first part we present the study of the leptonic decays B0 → e +e-, B0 → μ +μ- and B0 → e±μ∓, based on a dataset corresponding to (383.6 ± 4.2) × 106 BB¯ pairs. We do not find evidence of any of the three decay modes, and obtain upper limit on the branching fractions, at 90% confidence level, of [special characters omitted](B0 → e +e-) < 11.3 × 10-8 , [special characters omitted](B0 → μ+μ -) < 5.2 × 10-8, and [special characters omitted](B0 → e ±μ∓) < 9.2 × 10-8. In the second part we present the measurement of CP asymmetry in rare inclusive B → Xsγ decays on the recoil of fully-reconstructed hadronic B decays, using a dataset corresponding to (465.0 ± 5.1) × 106 BB¯ pairs. We measure a value of ACP = -0.12 ± 0.11 ± 0.03.