Proton Electromagnetic Form Factors in the Time-like Region through the Scan Technique

TL;DR

This review summarizes recent experimental measurements of proton time-like electromagnetic form factors, especially from BESIII, and discusses future prospects and theoretical models to better understand proton structure.

Contribution

It provides a comprehensive overview of recent high-precision measurements and introduces new theoretical models inspired by experimental results.

Findings

High-precision BESIII measurements of $e^{+}e^{-} o par{p}$

Comparison of recent results with previous measurements

Discussion of future measurements by the PANDA experiment

Abstract

For over 100 years, scientists have investigated the properties of the proton, which is one of the most abundant components of visible matter in the universe. Nevertheless, researchers do not fully understand many details about its internal structure and dynamics. Time-like electromagnetic form factors are one of the observable quantities that can help us achieve a deeper understanding. In this review article, we present an overview of the current experimental status in this field, consisting of measurements of the time-like reactions $e^{+}e^{-}\to p\bar{p}$, $p\bar{p}\to e^{+}e^{-}$, and future measurements of $p\bar{p}\to \mu^{+}\mu^{-}$. A focus is put on recent high precision results of the reaction $e^{+}e^{-}\to p\bar{p}$ that have been obtained after analyzing 688.5~pb$^{-1}$ of data taken at the BESIII experiment. They are compared and put into perspective to results from previous measurements in this channel. We discuss the channels $p\bar{p}\to e^{+}e^{-}$ and $p\bar{p}\to\mu^{+}\mu^{-}$ in terms of the few existing as well as future measurements, which the PANDA experiment will perform. Finally, we review several new theoretical models and phenomenological approaches inspired by the BESIII high precision results and then discuss their implications for a deeper understanding of the proton's structure and inner dynamics.