Measurement of the η and η′ transition form factors at q2=112 GeV2

Le résumé fourni par la source

We report a study of the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\gamma}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\gamma}$ at a center-of-mass energy of 10.58 GeV, using a $232\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample collected with the BABAR detector at the PEP-II collider at SLAC. We observe ${20}_{\ensuremath{-}5}^{+6}\ensuremath{\eta}\ensuremath{\gamma}$ and ${50}_{\ensuremath{-}7}^{+8}{\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\gamma}$ events over small backgrounds, and measure the cross sections $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}\ensuremath{\gamma})={4.5}_{\ensuremath{-}1.1}^{+1.2}\ifmmode\pm\else\textpm\fi{}0.3\text{ }\text{ }\mathrm{fb}$ and $\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\gamma})=5.4\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\pm\else\textpm\fi{}0.3\text{ }\text{ }\mathrm{fb}$. The corresponding transition form factors at ${q}^{2}=112\text{ }\text{ }{\mathrm{GeV}}^{2}$ are ${q}^{2}|{F}_{\ensuremath{\eta}}({q}^{2})|=0.229\ifmmode\pm\else\textpm\fi{}0.030\ifmmode\pm\else\textpm\fi{}0.008\text{ }\text{ }\mathrm{GeV}$, and ${q}^{2}|{F}_{{\ensuremath{\eta}}^{\ensuremath{'}}}({q}^{2})|=0.251\ifmmode\pm\else\textpm\fi{}0.019\ifmmode\pm\else\textpm\fi{}0.008\text{ }\text{ }\mathrm{GeV}$, respectively.

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