Improved measurement of the branching fraction and energy spectrum of η′ from Υ(1S) decays

We present an improved measurement of the η′ meson energy spectrum in Υ(1S) decays, using 1.2fb-1 of data taken at the Υ(1S) center-of-mass energy with the CLEO III detector. We compare our results with models of the η′ gluonic form factor that have been suggested to explain the unexpectedly large B→η′Xs rate. Models based on perturbative QCD fail to fit the data for large η′ energies, and thus an explanation outside the realm of the Standard Model or an improved understanding of nonperturbative QCD effects may be needed to account for this large rate.