Data Analysis and Preliminary Results of the Proton Charge Radius Experiment (PRad) at JLab

In order to investigate the proton radius puzzle, the PRad experiment (E12-11-106\footnote{Spokespersons: A. Gasparian (contact), H. Gao, M. Khandaker, D. Dutta}) was performed in 2016 in Hall B at Jefferson Lab, with 1.1 and 2.2 GeV unpolarized electron beam on a windowless H$_2$ gas flow target. The experiment aims to extract the electric form factor of the proton in an unprecedented low squared momentum transfer region ($\rm{Q}^2 = 2\times10^{-4} - 0.06~\rm{(GeV/c)}^2$), with a sub-percent precision. The PRad experiment utilizes a non-magnetic calorimetric method with a large acceptance and high resolution calorimeter (HyCal), and two large area, high spatial resolution Gas Electron Multiplier (GEM) detectors. To control the systematic uncertainties, the absolute $e-p$ elastic scattering cross section is normalized to that of the well-known M$\o$ller scattering process, which is measured simultaneously within similar kinematics and experimental acceptances. Both the luminosity and the energy independent part of the detector acceptance and efficiency are canceled out in the ratio. In this talk, we will discuss details of the data analysis and present the preliminary physics results from the 2.2 GeV data.