Theory of Beauty Lifetimes

A critical review of the theoretical understanding of the lifetimes of beauty hadrons is given. A model-independent analysis using the heavy-quark expansion allows for a description of the lifetime ratios (B )= (B 0 )a nd(b)= (B 0 )i n as mall region of parameter space. It is demonstrated that the lifetime ratio (B )= (B 0 ) cannot be used to extract the decay constant of the B meson. Implications for the semileptonic branching ratio and charm yield in B decays are pointed out.