High Precision Measurement of the Proton Charge Radius

We propose to perform a high precision e − p elastic cross sections measurement at very low four-momentum transfer squared, Q, from 10−4 to 10−2 (GeV/c) range using a high resolution calorimeter. The absolute value of the e−p cross sections will be controlled by a well known QED process, the Møller scattering, which will be continuously measured in this experiment within similar kinematics and the same experimental acceptances. The high precision differential cross sections, measured for the first time in this low Q range, will allow a sub-percent and essentially model independent extraction of the proton charge radius. With that, this experiment will have a direct impact on the “proton charge radius crisis” currently developing in hadronic and atomic physics. We propose to perform this experiment in Hall B at Jefferson Lab using the unique lowintensity electron beam control capabilities of the hall and part of the PrimEx-II infrastructure.