Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII

Abstract

The electromagnetic process e(+)e(-) -> p (p) over bar over bar is studied with the initial-state-radiation technique using 7.5 fb(-1) of data collected by the BESIII experiment at seven energy points from 3.773 to 4.600 GeV. The Born cross section and the effective form factor of the proton are measured from the production threshold to 3.0 GeV/c(2) using the p (p) over bar over bar invariant-mass spectrum. The ratio of electric and magnetic form factors of the proton is determined from the analysis of the proton-helicity angular distribution. (C) 2021 The Author. Published by Elsevier B.V.