Study of high momentum eta' production in B -> eta' X_s
  We measure the branching fraction for the charmless semi-inclusive process B -> eta' X_s, where the eta' meson has a momentum in the range 2.0 to 2.7 GeV/c in the Upsilon(4S) center-of-mass frame and X_s represents a system comprising a kaon and zero to four pions. We find B(B -> eta' X_s)=(3.9+/-0.8(stat)+/-0.5(syst)+/-0.8(model)).10^{-4}. We also obtain the X_s mass distribution and find that it tends to favor models predicting high masses. 
B. Aubert, et al, BABAR Collaboration