Study ofe+e−→pp¯using initial state radiation withBABAR

The $e^{+}{e}^{-}\to p\overline{p}$ cross section is determined over a range of $p\overline{p}$ masses, from threshold to $4.5\mathrm{GeV}/c^2$, by studying the $e^{+}{e}^{-}\to p\overline{p}\gamma$ process. The data set corresponds to an integrated luminosity of $232{\mathrm{fb}}^{-1}$, collected with the BABAR detector at the PEP-II storage ring, at an $e^{+}{e}^{-}$ center-of-mass energy of 10.6 GeV. The mass dependence of the ratio of electric and magnetic form factors, $|G_E/G_M|$, is measured for $p\overline{p}$ masses below $3\mathrm{GeV}/c^2$; its value is found to be significantly larger than 1 for masses up to $2.2\mathrm{GeV}/c^2$. We also measure $J/\psi \to p\overline{p}$ and $\psi (2S)\to p\overline{p}$ branching fractions and set an upper limit on $Y(4260)\to p\overline{p}$ production and decay.