Theoretical Aspects of Heavy Flavour Physics

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I review the status of theoretical aspects of B-decays. The principal difficulty in interpreting the wealth of experimental data is the control of non-perturbative QCD effects, and the talk is focused on attempts to control these effects. Lattice results for the decay constants, B- B mixing and semileptonic form-factors are summarized. The discrepancy of the theoretical predictions and experimental measurements for the ratio of lifetimes τ(Λb)/τ(B₀) is discussed, as well as the status of the semileptonic branching ratio of the B-meson. The difficulties in making quantitative predictions for exclusive nonleptonic decays are stressed, and some recent approaches to this problem are outlined.