Study of e+e- --> p anti-p via initial-state radiation at BABAR

TL;DR

This study measures the cross section and form factors of e+e- annihilation into proton-antiproton pairs using initial-state radiation at BABAR, providing detailed energy dependence and decay branching fractions.

Contribution

It provides new measurements of the energy dependence of the e+e- --> p anti-p cross section, form factor ratios, and decay branching fractions at energies from threshold to 4.5 GeV.

Findings

Measured cross section energy dependence from threshold to 4.5 GeV.

Determined the ratio |G_E/G_M| for p anti-p below 3 GeV.

Measured branching fractions for J/psi and psi(2S) decays to p anti-p.

Abstract

The process e+e- --> p anti-p gamma is studied using 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider, at an e+e- center-of-mass energy of 10.6 GeV. From the analysis of the p anti-p invariant mass spectrum, the energy dependence of the cross section for e+e- --> p anti-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 anti-p masses below 3 GeV. We also measure the branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti p.