Study of CP violation with charmonium-k*(892) channels by a full-angular time-dependent analysis (BaBar experiment)

This thesis presents the full-angular time-dependent analysis of the vector-vector channel B⁰_d → J/ψ(K_s⁰π⁰)*⁰. After a review of the CP violation in the B meson system, the phenomenology of the charmonium-K*(892) channels is exposed. The method for the measurement of the transversity amplitudes of the B → J/ψK*(892), based on a pseudo-likelihood method, is then exposed. The results from a 81.9 fb^-1 of collected data by the BABAR detector at the Υ(4S) resonance peak are |A₀|² = 0.565 ± 0.011 ± 0.004, |A(parallel)|² = 0.206 ± 0.016 ± 0.007, |A(perpendicular)|² = 0.228 ± 0.016 ± 0.007, δ(parallel) = - 2.766 ± 0.105 ± 0.040 and δ(perpendicular) = 2.935 ± 0.067 ± 0.040. Note that (δ(parallel),δ(perpendicular)) → (-δ(parallel), π - δ(perpendicular)) is also a solution. The strong phases δ(parallel) and δ(perpendicular) are at ∼≥ 3σ from ±π, signing the presence of final state interactions and the breakdown of the factorization hypothesis. The forward-backward analysis of the Kπ mass spectrum revealed the presence of a coherent S-wave interfering with the K*(892). It is the first evidence of this wave in the Kπ system coming from a B meson. The particularity of the B⁰_d → J/ψ(K_s⁰π⁰)*⁰ channel is to have a time-dependent but also an angular distribution which allows to measure sin(2β) but also cos(2β). The results from an unbinned maximum likelihood fit are sin(2β) = -0.10 ± 0.57 ± 0.14 and cos(2β) = 3.32_-0.96^+0.76 ± 0.27 with the transversity amplitudes fixed to the values given above. The other solution for the strong phases flips the sign of cos(2β). Theoretical considerations based on the s-quark helicity conservation favor the choice of the strong phases given above, leading to a positive sign for cos(2β). This sign of cos(2β) is the one predicted by the Standard Model. (author)