ITP-SB-93-41 Predictions for Semileptonic Decays ¯ B → D(D ∗)πℓ¯ν and Weak

The semileptonic decays B̄ → D(D)πlν̄ are analyzed by heavy quark and chiral symmetries. The branching ratio is of order of a few percent for B̄ → Dπlν̄, but it is much smaller for B̄ → Dπlν̄, of order 10−4− 10. The decay mode B → Dπeν̄e provides a nice place for extracting the DDπ coupling constant from the semileptonic decays of a B̄ meson. Two types of weak radiative decays of B̄ mesons and bottom baryons are studied. The decay Λ0b → Λγ receives the electromagnetic penguin b → sγ contribution and has a branching ratio of order 2×10−5. The radiative decays B̄ → Dγ, Λ0b → Σ0cγ, Ξ0b → Ξ0cγ and Ξ0b → Ξ0cγ occur through W exchange accompanied with a photon emission and their branching ratios are estimated to be much smaller. We conclude that the weak radiative decays of bottom hadrons are dominated by the short-distance electromagnetic penguin mechanism. Talk presented at the 5th International Symposium on Heavy Flavour Physics, Montreal, July 6-10, 1993.