Heavy quark decay

Exclusive D and B meson semileptonic branching ratio measurements are summarized and compared with models. In the D meson sector study of the ratio of rates of Kℓ⁺ν K^*ℓ⁺ν and the K^* polarization are in disagreement with most models, while in the B sector studies of similar final states are in agreement with the models. By comparing the D^*0ℓ^-ν and D^*+ℓ^-ν rates, the lifetime ratio of neutral and charged B's is shown to be equal to 1.18±0.27^+0.22_-0.30. Using this lifetime ratio, coupled with a new measurement of the fraction of neutral B's on the T(4S), the B⁰-B⁰ mixing parameter r is determined to be in the range 0.15 > r > 0.39. A hint of a positive signal for the b→u transition using the endpoint of the lepton momentum spectrum is shown to be consistent in the standard model with the mixing measurement and CP violation in the kaon sector. Finally indirect measurements of the absolute branching ratios for Λ_c→pK^-π⁺ and D_s→Θπ⁺ yield 4.1±1.5% and 1.5±0.8%, respectively.