Study of e+e-→pp¯ via initial-state radiation at BABAR

Abstract

The process e + e − → p ¯ p γ is studied using 469 fb − 1 of integrated luminosity collected with the BABAR detector at the SLAC National Accelerator Laboratory, at an e + e − center-of-mass energy of 10.6 GeV. From the analysis of the p ¯ p invariant mass spectrum, the energy dependence of the cross section for e + e − → p ¯ p is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, | G E / G M | , and the asymmetry in the proton angular distribution are measured for p ¯ p masses below 3 GeV. The branching fractions for the decays J / ψ → p ¯ p and ψ ( 2 S ) → p ¯ p are also determined.