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

Le résumé fourni par la source

We present an improved measurement of the ${\ensuremath{\eta}}^{\ensuremath{'}}$ meson energy spectrum in $\ensuremath{\Upsilon}(1S)$ decays, using $1.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data taken at the $\ensuremath{\Upsilon}(1S)$ center-of-mass energy with the CLEO III detector. We compare our results with models of the ${\ensuremath{\eta}}^{\ensuremath{'}}$ gluonic form factor that have been suggested to explain the unexpectedly large $B\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{X}_{s}$ rate. Models based on perturbative QCD fail to fit the data for large ${\ensuremath{\eta}}^{\ensuremath{'}}$ 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.

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