Charged pion form factor between $Q^2$=0.60 and 2.45 GeV$^2$. I. Measurements of the cross section for the ${^1}$H($e,e'\pi^+$)$n$ reaction

TL;DR

This paper reports precise measurements of the charged pion form factor by analyzing cross sections of the ${^1}$H($e,e'\pi^+$)$n$ reaction over a range of $Q^2$ values, providing insights into pion structure.

Contribution

It provides high-precision separated cross sections for the reaction at multiple $Q^2$ values, enabling detailed comparison with theoretical models of the pion form factor.

Findings

Cross sections measured with high precision across $Q^2$ range

Separated structure functions $\sigma_L$, $\sigma_T$, $\sigma_{LT}$, $\sigma_{TT}$ obtained

Data compared with theoretical models to extract pion form factor

Abstract

Cross sections for the reaction ${^1}$H($e,e'\pi^+$)$n$ were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF high-intensity, continous electron beam in order to determine the charged pion form factor. Data were taken for central four-momentum transfers ranging from $Q^2$=0.60 to 2.45 GeV$^2$ at an invariant mass of the virtual photon-nucleon system of $W$=1.95 and 2.22 GeV. The measured cross sections were separated into the four structure functions $\sigma_L$, $\sigma_T$, $\sigma_{LT}$, and $\sigma_{TT}$. The various parts of the experimental setup and the analysis steps are described in detail, including the calibrations and systematic studies, which were needed to obtain high precision results. The different types of systematic uncertainties are also discussed. The results for the separated cross sections as a function of the Mandelstam variable $t$ at the different values of $Q^2$ are presented. Some global features of the data are discussed, and the data are compared with the results of some model calculations for the reaction ${^1}$H($e,e'\pi^+$)$n$.