Soft gluon contributions to the B --> K eta' amplitude in a low energy   bosonization model
  Intriguing B --> K eta' decays provide a unique opportunity to study a joining of two-gluon configurations arising from the penguin b --> sG and b --> sGG transitions, with those inherent to the eta' particle. We employ the heavy-light chiral quark model, applied previously to a somewhat related B --> D eta' decay, as a calculational tool accounting for the nonperturbative soft gluon contributions to the amplitude at hand. Thereby we arrive at a novel contribution to the singlet penguin amplitude, which within our model accounts for ~ 10 % of the measured B --> K eta' amplitude. 
J. O. Eeg, K. Kumericki, I. Picek