B/b̄ Flavour Tagging and Doubly Charmed B Decays in Aleph

This contribution concerns three contributed papers that share the common feature of analysing fully(or almost fully-) reconstructed B decays coming from a sample of four million hadronic Z decays collected with the ALEPH detector at LEP. In the first paper 1, 404 charged and neutral B mesons decaying in standard modes are fully reconstructed and used to look for resonant structure in the Bπ± system. In the framework of Heavy Quark Symmetry (HQS), the mass of the B2 state and the relative production rate of the B∗∗ system are measured. In the same sample of B mesons, significant Bπ± charge-flavour correlations are observed. In the second paper 2, a search for doubly-charmed B decays with both charmed mesons reconstructed is performed. A clear signal is observed in the channels b → DsD̄(X) and b → DD̄(X) providing the first direct evidence for doubly-charmed b decays involving no Ds production. Evidence for associated KS and K ± production in the decays B → DD̄(X) is also presented and some candidates for completely reconstructed B meson decays B → DsD̄(nπ), B → DD̄KS and B → DD̄K ± are observed. Furthermore, candidates for the two-body Cabibbo suppressed decays B0 → D∗−D∗+ and B− → D(∗)0D(∗)− are also observed. One Bs → D + s D − s event is reconstructed, which can be only the short-lived CP even eigenstate. In the third paper 3, the Bs decay to D (∗)+ s D (∗)− s (X) is observed, tagging the final state with two φ in the same hemisphere. It corresponds mostly to the short-lived CP even eigenstate. A preliminary value of the Bs short lifetime is obtained.