Penguins with Charm and Quark-Hadron Duality

Abstract

The integrated branching fraction of the process $B\to X_s{l}^{+}{l}^{-}$ is dominated by resonance background from narrow charmonium states, such as $B\to X_s\ddot{I}ˆ\to X_s{l}^{+}{l}^{-}$, which exceeds the non-resonant charm-loop contribution by two orders of magnitude. The origin of this fact is discussed in view of the general expectation of quark-hadron duality. The situation in $B\to X_s{l}^{+}{l}^{-}$ is contrasted with charm-penguin amplitudes in two-body hadronic B decays of the type $B\to \ddot{I}€\ddot{I}€$, for which it is demonstrated that resonance effects and the potentially non-perturbative $c\bar{c}$ threshold region do not invalidate the standard picture of QCD factorization. This holds irrespective of whether the charm quark is treated as a light or a heavy quark.

20 pages, 4 figures