Measurement of theγγ*→π0transition form factor

We study the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ in the single tag mode and measure the differential cross section $d\ensuremath{\sigma}/d{Q}^{2}$ and the $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}$ transition form factor in the momentum transfer range from 4 to $40\text{ }\text{ }{\mathrm{GeV}}^{2}$. At ${Q}^{2}>10\text{ }\text{ }{\mathrm{GeV}}^{2}$ the measured form factor exceeds the asymptotic limit predicted by perturbative QCD. The analysis is based on $442\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity collected at PEP-II with the BABAR detector at ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energies near 10.6 GeV.

Measurement of theγγ*→π0transition form factor | Litlas