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

TL;DR

This paper reports precise measurements of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII, providing insights into proton structure at various energies.

Contribution

First measurement of proton form factors in the time-like region using initial state radiation at BESIII with detailed angular analysis.

Findings

Proton form factors measured from threshold to 3.0 GeV/$c^{2}$

Ratio of electric to magnetic form factors determined

Cross sections and form factors consistent with theoretical models

Abstract

The electromagnetic process $e^{+}e^{-}\to p\bar{p}$ 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 $p\bar{p}$ 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.