Kolya Uraltsev was one of the inventors of the Heavy Quark Expansion (HQE), that describes inclusive weak decays of hadrons containing heavy quarks and in particular lifetimes. Besides giving a pedagogic introduction to the subject, we review the development and the current status of the HQE, which just recently passed several non-trivial experimental tests with an unprecedented precision. In view of many new experimental results for lifetimes of heavy hadrons, we also update several theory predictions: [Formula: see text], τ(Bs)/τ(Bd) = 1.001 ±0.002, τ(Λb)/τ(Bd) = 0.935 ±0.054 and [Formula: see text]. The theoretical precision is currently strongly limited by the unknown size of the non-perturbative matrix elements of four-quark operators, which could be determined with lattice simulations.
Heavy quark symmetry and weak decays of thebbaryons in pentaquarks with acc¯component