New fit of timelike proton electromagnetic formfactors from e+e− colliders

E Tomasi-Gustafsson,Simone Pacetti,Andrea Bianconi

doi:10.1103/physrevc.103.035203

Abstract

The data on the proton form factors in the time-like region from the BaBar, BESIII and CMD-3 Collaborations are examined to have coherent pieces of information on the proton structure. Oscillations in the annihilation cross section, previously observed, are determined with better precision. The moduli of the individual form factors, determined for the first time, their ratio and the angular asymmetry of the annihilation reaction $e^+e^-\to\bar p p$ are discussed. Fiits of the available data on the cross section, the effective form factor, and the form factor ratio, allow to propose a description of the electric and magnetic time-like form factors from the threshold up to the highest momenta.

Highlights

The understanding of the proton electromagnetic form factors (FFs), called electric GE (q2) and magnetic GM (q2) Sachs FFs is the aim of theoretical and experimental studies for decades, in the frame of a unified view of the scattering and annihilation regions
Much progress has been performed recently due, on one side, to new experiments that collected information with better precision and/or in a wider kinematical range and, on the other side, to theoretical efforts that extend models and parametrizations built in the spacelike (SL) region to the timelike (TL) region
Models based on dispersion relations [3] or vector dominance [4,5] have attempted a global description in SL and TL regions

Summary

Introduction

The understanding of the proton electromagnetic form factors (FFs), called electric GE (q2) and magnetic GM (q2) Sachs FFs is the aim of theoretical and experimental studies for decades, in the frame of a unified view of the scattering and annihilation regions. Much progress has been performed recently due, on one side, to new experiments that collected information with better precision and/or in a wider kinematical range and, on the other side, to theoretical efforts that extend models and parametrizations built in the spacelike (SL) region to the timelike (TL) region Not all models developed in the SL region have the correct analytical properties to be extended in the TL region where FFs are of complex nature [6].

Objectives

Methods

Conclusion