Measurement of the γγ*→ηc transition form factor

Le résumé fourni par la source

We study the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\eta}}_{c}$, ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{K}_{S}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and obtain ${\ensuremath{\eta}}_{c}$ mass and width values $2982.2\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\pm\else\textpm\fi{}1.6\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $31.7\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\pm\else\textpm\fi{}0.8\text{ }\text{ }\mathrm{MeV}$, respectively. We find $\ensuremath{\Gamma}({\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})\mathcal{B}({\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}K\overline{K}\ensuremath{\pi})=0.374\ifmmode\pm\else\textpm\fi{}0.009\ifmmode\pm\else\textpm\fi{}0.031\text{ }\text{ }\mathrm{keV}$, and measure the $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}$ transition form factor in the momentum transfer range from 2 to $50\text{ }\text{ }{\mathrm{GeV}}^{2}$. The analysis is based on $469\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity collected at PEP-II with the BABAR detector at ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energies near 10.6 GeV.

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