Study of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup><mml:mo>→</mml:mo><mml:mi>p</mml:mi><mml:mover accent="true"><mml:mi>p</mml:mi><mml:mo>¯</mml:mo></mml:mover></mml:math>using initial state radiation with<i>BABAR</i>

Abstract

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