# Study of the process $e^+ e^- \to p \bar p$ via initial state radiation at BESIII

## TL;DR

This paper measures the cross section and form factors of the process $e^+ e^- o p ar p$ using initial state radiation at BESIII, providing detailed insights into proton structure in the 2.0-3.8 GeV/$c^2$ range.

## Contribution

It presents the first detailed measurement of the proton form factor ratio and cross section in this energy range using initial state radiation at BESIII.

## Key findings

- Proton effective form factor was determined across the mass range.
- The proton form factor ratio was measured in specific mass intervals.
- The cross section for $e^+ e^- o p ar p$ was precisely measured.

## Abstract

The Born cross section for the process $e^+ e^- \to p \bar p $ is measured using the initial state radiation technique with an undetected photon. This analysis is based on datasets corresponding to an integrated luminosity of 7.5 fb$^{-1}$, collected with the BESIII detector at the BEPCII collider at center of mass energies between 3.773 and 4.600 GeV. The Born cross section for the process $e^+ e^- \to p \bar p $ and the proton effective form factor are determined in the $p\bar p$ invariant mass range between 2.0 and 3.8 GeV/$c^2$ divided into 30 intervals. The proton form factor ratio ($|G_E|/|G_M|$) is measured in 3 intervals of the $p\bar p$ invariant mass between 2.0 and 3.0 GeV/$c^2$.